Method and system for managing light at an optical interface

ABSTRACT

An interface between two different optical materials can comprise a stack of thin film layers that manage light incident on that interface. One of the optical materials can have a first composition and a first refractive index, while the other optical material can have a second composition and a second refractive index. The stack can comprise thin film layers of the first optical material interleaved between thin film layers of the second optical material. The layers of the stack can be configured to provide the stack with an aggregate composition of at least one of the optical materials that progressively varies from one end of the stack to the other end. To provide the progressive variation in composition, the layers of one of the optical materials can have a progressively increased thickness across the stack, or can progressively increase in number, for example.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 12/931,191 filed on Jan. 26, 2011 in the name ofMichael L. Wach and entitled “Method and System for Managing Light at anOptical Interface” (U.S. Pat. No. 8,116,003, issue date Feb. 14, 2012);which is a continuation of and claims priority to U.S. patentapplication Ser. No. 11/825,614, entitled “Method and System forManaging Light at an Optical Interface,” filed on Jul. 7, 2007 in thename of Michael L. Wach, (now U.S. Pat. No. 7,903,338); which claimspriority to U.S. Provisional Patent Application No. 60/819,552, filedJul. 8, 2006 in the name of Michael L. Wach and entitled “Method andSystem for Managing Light at an Optical Interface.” The presentapplication claims priority to each of the above identified patentapplications. The entire contents of each of the above identifiedpriority documents (including U.S. patent application Ser. Nos.12/931,191 and 11/825,614 and U.S. Provisional Patent Application No.60/819,552) are hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to optical devices and more specificallyto thin film optical systems that manage light at an interface betweentwo optical materials that have distinct compositions or differentrefractive indices.

BACKGROUND

Thin films are useful for a wide range of optical applications, such asantireflective (“AR”) coatings, high-reflective (“HR”) coatings,dielectric mirrors, thin film interference filters, active lightemitters, gratings, and color generators, to name a few examples.Compact size and environmental stability are two properties of opticalthin films that encourage their deployment in modern applicationsincluding optical communications, lighting, vision, instrumentation,medical devices, computer monitors, display systems, etc. Certain typesof optical thin films manipulate light by interference, which entails anadditive or subtractive process in which the amplitudes of two or moreoverlapping light waves systematically attenuate or reinforce oneanother. Interference can produce polarization, wavelength-selectivetransmission and/or reflection, beam splitting, or various other effectson a light beam, according to the design of the thin film and itsinteraction with adjacent elements in an environment of an opticalsystem.

Thin film interference filters typically comprise a stack of thin filmlayers or a plurality of laminates that collaboratively provide a band,span, or range of color transmission and another band, span, or range ofcolor reflection. Such thin film interference filters often provide apass band that is bracketed by two bands of reflection. That is, aspectral or color region of high transmission (and low reflectivity)lies between two spectral or color regions of low transmission (and highreflectivity). Many conventional interference filters are better suitedto providing a pass band or a narrow spectral band of high transparencythan to providing a stop band or a narrow spectral band of highreflectivity, sometimes referred to as a notch.

FIG. 3A illustrates a cross sectional view of a portion 325 of aconventional thin film apparatus, for example a band pass filter,comprising a first layer of optical material 360 adhering or laminatedto a second layer of optical material 370. The accompanying FIG. 3Bgraphically depicts a representative refractive index profile 300 forthe materials 360, 370 illustrated in FIG. 3B.

The optical materials 360, 370 typically have different refractiveindices 310, 320, for example one being relatively high and one beingrelatively low. The material 370 might be silicon dioxide (SiO₂), ofrelatively low refractive index 320, while the material 360 might betantalum pentoxide (Ta₂O₅), of relatively high refractive index 310. Inthe conventional approach, each material layer 360, 370 typically has athickness at least on the order of one-fourth of the wavelength of thelight that the system 325 handles.

The interface 340 lies between two materials 360, 370, with FIG. 3illustrating two more interfaces 330, 350. As shown in FIG. 3B, therefractive index typically changes abruptly at the boundaries orinterfaces 330, 340, 350 between each layer of the material 360 and thematerial 370. Thus, the system 325 typically has a crisp change in thematerial composition between the two material regions 360, 370.

The refractive index change between the two materials 360, 370, at theinterface 340, can usefully induce a light reflection that, whencombined with reflections from other interfaces 330, 350, producesoptical interference. However in some applications, a more graduallychange in refractive index at the interfaces 330, 340, 350 would bedesirable. For example, thin film notch filters that produce a narrowspectral band of reflection between two spectral regions of transmissionmay benefit from having gradual changes in refractive index at layerboundaries.

A class of notch filters known as “rugate” filters typically use aconventional approach to providing a gradual refractive index change ata filter's thin film layer interfaces. In a rugate filter, eachinterface between adjoining thin film layers typically comprises ablended combination of the materials of the two adjoining layers. Thatis, if the apparatus 325 illustrated in FIG. 3A was a rugate filter, theinterface 340 would have a composition that gradually changed betweenthe material 370 and the material 360 (along the Z axis).

Rugate filters are typically fabricated in a vacuum chamber via thinfilm deposition. A source in the chamber outputs particles ofhigh-refractive index material that accumulate to create thehigh-refractive index layers. Another source outputs particles oflow-refractive index materials to create the adjoining low-refractiveindex layers. When forming the rugate's blended interface, both thehigh-refractive index source and the low-refractive index source mayactively output their respective materials. After forming the majorportion of the high-refractive index layer, the high-refractive indexsource gradually reduces its rate of outputting high-refractive indexparticles. As the deposition rate of high-refractive index particlesdecreases, the low-refractive index source begins outputtinglow-refractive index particles and gradually increases the depositionrate of low-refractive index particles. Accordingly, the rugate'sblended interface can be formed by simultaneously depositing high- andlow-index materials at controlled deposition rates.

However, with conventional technologies, providing a sufficient level ofcontrol of the deposition rates can be difficult. If the relativedeposition rates of the high- and low-index materials are not preciselycontrolled, the rugate's blended layer interfaces may fail to providethe desired optical properties. Another problem with many conventionaltechniques for producing rugate filters can occur with the materialproperties that result from the blended composition itself. Twomaterials that are individually well suited to forming pure layers maynot be compatible with one another when mixed. That is, although twopure material layers may adhere to one another, those two materials maynot form a stable or robust structure when blended or when mixed at theatomic, molecular, or particulate level. For example, the blendedcomposition may have thermal expansion properties or sensitivities thatare less desirable than the corresponding properties of unblendedlayers. Further, processing the appropriate materials in a manner thatfacilitates successful blending can be problematic.

To address these representative deficiencies in the art, what is neededis an improved capability for managing light propagating near aninterface between two optical materials or media. A further need existsfor a structure that can provide a smooth or gradual refractive indextransition between two materials. Yet another need exists for a systemthat can provide a smooth material transition at an interface betweentwo sections of distinct optical materials. Still another need existsfor an efficient or robust process to fabricate thin film devices in amanner that provides desirable interfaces between adjoining film layers.One more need exists for a notch filter that offers a high level ofoptical performance, that provides a low level of environmental and/orthermal sensitivity, and that can be cost-effectively manufactured.Finally, a need exists for a process of forming filters with rugate-typeoptical characteristics without necessarily blending optical materialsin a deposition chamber. A technology filling one or more of these needswould enhance the precision with which optical thin films manipulatelight and would facilitate cost-effective utilization of optical thinfilms in numerous applications.

SUMMARY

The present invention can support managing light in the vicinity of aninterface or a junction between two optical materials that have distinctmaterial compositions or optical characteristics, such as differentrefractive indices.

In one aspect of the present invention, an optical system that comprisesthin film layers can have a composition and/or an optical property thatvaries systemically along a direction that is perpendicular to thelayers (or essentially parallel to layer thickness). The optical systemcan comprise multiple thin film layers disposed to form a stack, aplurality of adjoining or abutting layers, a laminate structure, or someother ordered arrangement. Such a stack can comprise thin film layersthat have a first material composition interleaved or interspersedbetween thin film layers that have a second material composition. Forexample, with the possible exception of the layers at each end of thestack, each layer of the first material can be sandwiched between twolayers of the second material. Likewise and with the same potentialexception, each layer of the second material can be sandwiched betweentwo layers of the first material. Taken individually, each layer canhave a uniform or essentially homogeneous composition. Meanwhile, thestack can have a net or an aggregate composition that varies from oneend of the stack to the other end of the stack. That is, while the stackcan comprise two or more sets of thin film layers, each having anessentially common composition, the stack as a whole can have acomposition that progressively changes between each end of the stack.The aggregate compositional variation can impart the stack with acorresponding optical variation, such as a graduated refractive index.The end-to-end compositional variation can result from the configurationor arrangement of the individual layers of the stack. For example,varying the thicknesses of the individual layers can produce a definedcompositional pattern. The compositional variation might alternativelyresult from progressively increasing the number of layers of onematerial type towards one end of the stack.

A system that manages light near an interface between two opticallydissimilar materials can have numerous applications. To name a fewpotential applications, the system can benefit thin film interferencefilters, notch filters, band pass filters, dielectric filters, ripple orsidebands in light manipulation devices, dispersion characteristics,flat panel displays, antireflective coatings, optoelectronics devices,electro-optic materials, silicon photonic devices, gem stones, jewelry,charge coupled devices (“CCDs”), CCD pixels, laser cavities, opticalgain media, optical detectors, optical receivers that respond to changesin light intensity in advance of the light reaching the receiver,surgical lasing systems that apply dye to tissue to enhance interactionbetween the laser light and the tissue, tissue analyzers that referenceout the effect of blood on the tissue analysis by modulating blood flowduring analysis, diffractive mode expanders, planar lightguide circuits,optical fibers, lenses, optical properties of diamonds, analyticalsystems that characterize samples via analyzing light-matterinteractions, monofilament lines that have improved opticalcharacteristics, etc.

The discussion of optical thin films presented in this summary is forillustrative purposes only. Various aspects of the present invention maybe more clearly understood and appreciated from a review of thefollowing detailed description of the disclosed embodiments and byreference to the drawings and any claims that may follow. Moreover,other aspects, systems, methods, features, advantages, and objects ofthe present invention will become apparent to one with skill in the artupon examination of the following drawings and detailed description. Itis intended that all such aspects, systems, methods, features,advantages, and objects are to be included within this description, areto be within the scope of the present invention, and are to be protectedby the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B, collectively FIG. 1, illustrate an optical systemcomprising an optical thin film adhering to a substrate in accordancewith an exemplary embodiment of the present invention.

FIG. 2 illustrates a stack of optical thin films on a substrate inaccordance with an exemplary embodiment of the present invention.

FIGS. 3A and 3B, collectively FIG. 3, respectively illustrate a crosssection and a refractive index plot of a conventional stack of opticalthin film layers.

FIG. 4 illustrates a high-level plot of refractive index of a pluralityof thin film layers, generally resembling a smoothed square wave, inaccordance with an exemplary embodiment of the present invention.

FIG. 5 illustrates a high-level plot of refractive index of a pluralityof thin film layers, generally resembling a sinusoidal waveform, inaccordance with an exemplary embodiment of the present invention.

FIG. 6 illustrates a refractive index plot of a plurality of thin filmlayers, wherein a net or average refractive index profile overlays adetail plot that depicts the refractive index pattern of a series oftransition or transitional thin film layers disposed at an interfacebetween major thin film layers, in accordance with an exemplaryembodiment of the present invention.

FIG. 7 illustrates a refractive index plot of a plurality of thin filmlayers, wherein a net or average refractive index profile overlays adetail plot that depicts the refractive index pattern of a series oftransition or transitional thin film layers disposed at an interfacebetween major thin film layers, in accordance with an exemplaryembodiment of the present invention.

FIG. 8 illustrates a refractive index plot of a plurality of thin filmlayers, wherein a net or average refractive index profile overlays adetail plot that depicts the refractive index pattern of a series oftransition or transitional thin film layers disposed at an interfacebetween major thin film layers, in accordance with an exemplaryembodiment of the present invention.

FIG. 9 illustrates a refractive index plot of a plurality of thin filmlayers, wherein a net or average refractive index profile overlays adetail plot that depicts the refractive index pattern of a series oftransition or transitional thin film layers disposed at an interfacebetween major thin film layers, in accordance with an exemplaryembodiment of the present invention.

FIG. 10 illustrates a cross sectional profile of a plurality of thinfilm layers that manage light at an interface between two opticalmaterial sections in accordance with an exemplary embodiment of thepresent invention.

FIG. 11 illustrates a cross sectional profile of a plurality of thinfilm layers that manage light at an interface between two opticalmaterial sections in accordance with an exemplary embodiment of thepresent invention.

FIG. 12 illustrates a cross sectional profile of a plurality of thinfilm layers that manage light at an interface between two opticalmaterial sections in accordance with an exemplary embodiment of thepresent invention.

FIG. 13 illustrates a cross sectional profile of a plurality of thinfilm layers that manage light at an interface between two opticalmaterial sections in accordance with an exemplary embodiment of thepresent invention.

FIG. 14 illustrates a cross sectional profile of a plurality of thinfilm layers that manage light at an interface between two opticalmaterial sections in accordance with an exemplary embodiment of thepresent invention.

FIG. 15 illustrates a flowchart of a process for fabricating opticalcomponents that comprise a series of thin film layers that manage lightat an interface between two optical material sections in accordance withan exemplary embodiment of the present invention.

FIG. 16 illustrates a flowchart of a process for using a series of thinfilm layers to manage light at an interface between two optical materialsections in accordance with an exemplary embodiment of the presentinvention.

FIGS. 17A and 17B, collectively FIG. 17, respectively illustrate arepresentative perspective view and a functional block diagram of asystem for receiving light with a detector, wherein the system adjuststhe detector in advance of receiving the light in accordance with anexemplary embodiment of the present invention.

FIG. 18 illustrates a representative perspective view of a system forreceiving light, wherein the level of received light is adjusted inadvance of receiving the light in accordance with an exemplaryembodiment of the present invention.

FIG. 19 illustrates a timing diagram of a system for receiving lightwith a detector, wherein the system adjusts the detector's sensitivityin advance of receiving the light in accordance with an exemplaryembodiment of the present invention.

FIGS. 20A and 20B, collectively FIG. 20, illustrate a flowchart of aprocess for adjusting an optical detector, based on an intensity of anoptical signal, in advance of the detector receiving the optical signalin accordance with an exemplary embodiment of the present invention.

FIGS. 21A, 21B, and 21C, collectively FIG. 21, illustrate a gemstoneprior to and after applying an optical coating to a facet, wherein thecoating suppresses facet reflection in accordance with an exemplaryembodiment of the present invention.

FIG. 22 illustrates a flowchart of a process for using a thin filmcoating to suppress reflections from a facet of a gemstone and toenhance the gemstone's fire in accordance with an exemplary embodimentof the present invention.

FIG. 23 illustrates a system, comprising a series of apertures, havingprogressively increasing diameter, that perform a mode expansion onlight emitted from an optical fiber in accordance with an exemplaryembodiment of the present invention.

FIG. 24 illustrates a flowchart of a process for expanding a single modelight beam using diffraction associated with a series of progressivelylarger apertures in accordance with an exemplary embodiment of thepresent invention.

FIG. 25 illustrates a surgical system for cutting biological tissue byapplying a light absorber and laser light to the tissue in accordancewith an exemplary embodiment of the present invention.

FIG. 26 illustrates a flowchart of a process for cutting biologicaltissue by applying dye and laser light to the tissue in accordance withan exemplary embodiment of the present invention.

FIGS. 27A and 27B, collectively FIG. 27, illustrate a flowchart of aprocess for analyzing tissue of an organism via acquiring spectra fromthe tissue while modulating the tissue's blood content and using theacquired spectra to compensate for blood content in accordance with anexemplary embodiment of the present invention.

FIG. 28 illustrates an optical system for optically characterizing asample in accordance with an exemplary embodiment of the presentinvention.

FIG. 29 illustrates an optical system for optically characterizing asample in accordance with an exemplary embodiment of the presentinvention.

Many aspects of the invention can be better understood with reference tothe above drawings. The components in the drawings are not necessarilyto scale, emphasis instead being placed upon clearly illustrating theprinciples of exemplary embodiments of the present invention. Moreover,in the drawings, reference numerals designate like or corresponding, butnot necessarily identical, elements throughout the several views.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention can involve managinglight at an interface or a juncture between two optical materials, forexample to promote reflection, transmission, or transfer of light at theinterface. Various applications and system can benefit from managinglight at an optical interface.

A method and system for managing light at a material interface andcertain application examples will now be described more fullyhereinafter with reference to FIGS. 1, 2, and 4-27, which showrepresentative embodiments of the present invention. FIGS. 1 and 2depict thin film systems that adhere to substrates and that can comprisea thin film structure for managing light at an optical interface. FIGS.4-9 provide graphical refractive index profiles of thin film systemsthat manage light at an optical interface. FIGS. 10-14 provideillustrations of thin film systems that manage light at an opticalinterface. FIGS. 15 and 16 provide flow diagrams of methods for makingand operating thin film systems that manage light at an opticalinterface.

FIGS. 17-29 describe methods and systems that may involve a thin filmsystem managing light at an optical interface. FIGS. 17-20 relate to anoptical receiver that can prepare itself to receive an optical signal inadvance of receiving the optical signal. FIGS. 21-22 relate to treatinga gemstone to enhance the manner in which the gemstone dispersesincident light into a spectrum of colors. FIGS. 23 and 24 relate toexpanding a light beam using a series of progressively larger aperturesthat provide controlled diffraction. FIGS. 25-26 relate to applying alocal surface treatment to a biological tissue to enhance theinteraction between a surgical laser and the tissue. FIG. 27 relates tomodulating the blood content of a tissue volume of an organism tofacilitate conducting an analysis of the tissue and/or the blood. FIGS.28 and 29 relate to using light for material analysis.

The invention can be embodied in many different forms and should not beconstrued as limited to the embodiments set forth herein; rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thosehaving ordinary skill in the art. Furthermore, all “examples” or“exemplary embodiments” given herein are intended to be non-limiting,and among others supported by representations of the present invention.

Turning now to discuss each of the drawings presented in FIGS. 1-29, inwhich like numerals indicate like elements through the several figures,an exemplary embodiment of the present invention will be described indetail.

FIGS. 1A and 1B illustrate an exemplary thin film optical system 100comprising an optical thin film 110 adhering to a substrate 120according to an embodiment of the present invention. A Cartesiancoordinate system, having an x-axis 140, a y-axis 150, and a z-axis 130,illustrates the relative orientation of the optical thin film 110 andsubstrate 120 in the optical system 110. The x-axis 140 and the y-axis150 are parallel to the major surfaces 170, 180 of the optical thin film110, while the z-axis 130 traverses the thickness 160 of the opticalthin film 110. Those major surfaces 170, 180, whether planar orcontoured in a non-planar form, can be referred to as faces of theoptical thin film 110. That is, the z-axis 130 is perpendicular to theplanar interface 170 between the optical thin film 110 and the substrate120, while the x-axis 140 and the y-axis 150 lie in or along the planeof this interface 170.

The exemplary substrate 120 comprises a volume of optical materialtaking the general form of a slab with a smooth planar surface 170 towhich the optical thin film 110 adheres. In this configuration, thesubstrate 120 provides mechanical support and physical stability for theoptical thin film 110. Although FIG. 1 illustrates the optical thin film110 in a planar configuration, the optical thin film 110 canalternatively have a non-planar contour, for example conforming oradhering to a convex, cylindrical, or concave surface of a lens or someother passive or active device, in accordance with exemplary embodimentsof the present invention.

Functionally, a refractive index differential at the surface interfaceboundary 170 between the material of the optical thin film 110 and thematerial of the substrate 120 induces reflection of the light 125propagating through the thickness 160 of the optical thin film 110,generally along the z-axis 130. The outer surface 180 of the opticalthin film 110, opposite the substrate interface 170, is also reflectiveto light 125 propagating through the thickness 160 of the optical thinfilm 110. The outer surface's reflectivity can arise from the refractiveindex differential between the material of the optical thin film 110 andthe surrounding media 185. That is, the inner surface 170 and the outersurface 180 of the optical thin film 110 may individually reflect light125 propagating through the thickness 160 of the optical thin film 110.The degree of reflectivity of each of these surfaces 170, 180 can be afunction of the refractive index differential at or across each surface170, 180 and the angle of the incident light 125 relative to the z-axis130 and other potential factors, such as the polarization of the light125. The light 125 propagating through the optical thin film 110 maytravel parallel with the z-axis 130. Alternatively, the light 125 may beincident on the optical thin film 110 at an angle, such as an acuteangle, with respect to the z-axis 130.

The system 110 can comprise a thin film structure that manages light 125at the inner interface boundary 170 and/or the outer surface 180. Thatthin film structure can manage light flow, light passage, lightreflection, phase shift, or some other interaction or aspect of thelight 125 that is incident upon the inner and outer interfaces 110, 180.Moreover, the structure can provide an optical or material transitionbetween refractive indices of the substrate 120 and the thin film 110 orbetween the refractive indices of the thin film 110 and the surroundingmedium 185. In providing an optical or material transition, the thinfilm structure can effectively smooth the abrupt material and refractiveindex change of the interface 170 and the interface 180. Such a thinfilm structure can be referred to as transition layers or a transitiondevice, but may nonetheless have an expanded operability beyondfacilitating light transition. Thus, such a thin film structure can beviewed as transition layers that provide a useful influence over thelight 125 that is incident on the optical interface 170 and/or theoptical interface 180.

FIG. 1 does not illustrate the detailed structure of such transitionlayers but rather provides a somewhat macroscopic system-level view.However, the reference number “175” and the accompanying lead line showsone exemplary location for transition layers, specifically at thematerial interface 275.

As discussed in further detail below, the transition layers 175 cancomprise a plurality of thin film layers that are significantly thinnerthan the layer 110. FIGS. 6-14, discussed below, describe variousexemplary embodiments of the transition layers 175.

In one exemplary embodiment of the present invention, the thickness 160of the optical thin film 110 is less than approximately ten wavelengthsof the light 125 that the optical thin film 110 is operative tomanipulate. In one exemplary embodiment of the present invention, thethickness 160 of the optical thin film 110 is less than approximatelyfive wavelengths of the light 125 that the optical thin film 110 isoperative to manipulate. In one exemplary embodiment, the thickness 160is a physical thickness that can have a range of actual numerical valuesor may be less than approximately five times the wavelength of the light125 that the optical thin film 110 manipulates with thin filminterference.

In one exemplary embodiment of the present invention, the thickness 160of the optical thin film 110 is less than approximately threewavelengths of the light 125 that the optical thin film 110 is operativeto manipulate. In one exemplary embodiment of the present invention, thethickness 160 of the optical thin film 110 is less than approximatelyone wavelength of the light 125 that the optical thin film 110 isoperative to manipulate. In one exemplary embodiment of the presentinvention, the thickness 160 of the optical thin film 110 isapproximately one fourth the wavelength of the light 125 that theoptical thin film 110 is operative to manipulate. In one exemplaryembodiment of the present invention, the thickness 160 of the opticalthin film 110 is greater than approximately one nanometer and less thanapproximately ten microns. In various embodiment, the thickness of thetransition layers 175 can be one-fourth, one-tenth, one-fiftieth,one-hundredth, one-thousandth, or in a range thereof, of any of thesethicknesses 160 of the thin film layer 110. In various exemplaryembodiments, the thicknesses of the individual layers of the transitionlayers 175 can be one-fourth, one-tenth, one-fiftieth, one-hundredth,one-thousandth, or in a range thereof, of the total thickness of thetransition layers 175.

In addition to a physical thickness 160, the optical thin film 110 canhave an optical thickness that is a function of the refractive index ofthe material of the optical thin film 110 and the geometric or physicalthickness 160. The refractive index, or index of refraction, of amaterial is the speed of light in a vacuum divided by the speed of lightin the material. Since light propagates more slowly in ordinarymaterials than in a vacuum, the refractive index of an ordinary materialis greater than one, often between about one and four. The opticalthickness parameter is physical thickness 160 multiplied by refractiveindex. The optical thickness of a section of optical material, such asan optical thin film 110, is the material section's physical thickness160 multiplied by the material section's refractive index. Sincerefractive index is greater than one for normal optical materials, asection of ordinary material typically has an optical thickness that isgreater than its corresponding physical thickness 160.

The surrounding medium 185, which is in contact with the outer surface180 of the optical thin film 110, can be a range of one or more gaseous,liquid, or solid materials. In one exemplary embodiment of the presentinvention, the medium 185 is space, essentially void of matter. That is,the thin film 110 can operate in a vacuum environment. In one exemplaryembodiment of the present invention, the medium 185 is a gas, such asair, nitrogen, hydrogen, helium, oxygen, or a mixture of gases. In oneexemplary embodiment of the present invention, the medium 185 is anotheroptical thin film layer, such as a layer of a thin film interferencefilter. In one exemplary embodiment of the present invention, theoptical thin film 110 adheres to this medium 185 as well as to thesubstrate 120. In one exemplary embodiment of the present invention,this medium 185 is a liquid such as water, optical matching gel,matching fluid, a biological fluid, or hydrocarbon. Such biologicalfluids can include blood, saliva, cerebral spinal fluid (“CSF”),secretions, urine, or milk, any of which can be either in a processed ora natural form. The medium 185 can also be glass, a plastic, a rubber, acomposite, an inhomogeneous matrix, a resin, or an epoxy, any of whichcan be in a solid or viscous state. In one exemplary embodiment, thesystem 100 is encapsulated in plastic, for example via molding, with theplastic being the medium 185. In addition to passive materials, themedium 185 can be an active material such as a semiconductor detector,optically active material, electrically active material, optical gainmedium, or a silicon photonic material, for example. The medium 185 canalso be a biological composition such as a matrix of cells, tissue,tumorous material, muscular tissue, for example. In general, the medium185 is not limited to a specific material, or any of the materials orcompositions discussed herein.

In one exemplary embodiment of the present invention, the medium 185 issealed in a hermetic environment. The medium 185 can be the hermeticinternal environment of an electronic, optical, or optoelectronicpackage, for example a receiver, transmitter, or receiver module foroptical networking. In one exemplary embodiment of the presentinvention, the medium 185 resides in a sealed environment that is nothermetic, such as in a water-tight enclosure that is permeable togaseous contamination.

In one exemplary embodiment, the system 100 comprises a thin filminterference filter with the encapsulated in plastic, with the plasticencapsulating material comprising the medium 185. Transition layers (oran antireflective film) located adjacent the surface 180 can help managethe flow of light between the filter and the encapsulating material. Thestructure comprising the plastic and the filter can be deployed in atransmitter, a receiver, or a transceiver for an optical networkingapplication, such as fiber-to-the-home.

The refractive indices of the medium 185, the optical thin film 110, thesubstrate 120, the transition layers 175, and/or the individuals layersof the transition layers 175, can shift temporarily in response to anenvironmental change such as stress or operating temperature.Alternatively, these refractive indices can remain stable, experiencinglittle change in response to environment effects. In one exemplaryembodiment of the present invention, one or more of these refractiveindices can intentionally respond to a control input, which can be,without limitation, an electrical, magnetic, optical, or electromagneticfield, signal, or wave.

Light interference can result from additive or subtractive interactionbetween reflection at the outer surface 180 of the optical thin film 110and reflection at the inner surface 170 of the optical thin film 110.When these two reflections are in phase with one another, the amplitudesconstructively add. Alternatively, when the reflections are out of phasewith respect to one another, the amplitudes can destructively subtractor cancel one another. Such constructive and destructive interferencecan provide a wide assortment of optical effects. Exemplary effectsinclude filtering, polarizing, and dispersing light, among others.

The transition layers 175 can provide an heightened level of control ormanagement over the light interference associated with those surfaces170, 180. In one exemplary embodiment, the transition layers 175 cansuppress the interference. In one exemplary embodiment, the transitionlayers 175 can enhance or amplify the interference. In one exemplaryembodiment, the transition layers 175 can impart the interference withincreased selectivity in terms of wavelength, frequency, or color. Thatis, the transition layers 175 can provide precise wavelength, frequency,or color control over light interference that typically occurs inoptical thin film systems.

In one exemplary embodiment of the present invention, an operability ofthe optical thin film 110 to manipulate light 125 by thin filminterference is a function of or is related to one or more of: thethickness 160 of the optical thin film 110 in relation to thewavelengths of manipulated light 125; the spatial relationship orphysical separation between the outer surface 180 and the inner surface170; the refractive indices of the substrate 120, the optical thin film110, and the surrounding medium 185; the angle of the light 125 withrespect to the z-axis 130; the polarization of the light 125; and thetransition layers 175.

In one exemplary embodiment of the present invention, interference ofthe optical thin film 110 provides selective transmission light havingspecific wavelengths and reflection of the light that is nottransmitted. The transition layers 175 can enhance, control, orotherwise manage such interference, for example improving wavelengthselectivity of transmission and/or reflection.

In one exemplary embodiment of the present invention, the optical thinfilm 110 minimizes the reflection of light 125 incident on the substrate120, effectively countering the tendency of the refractive indexdifferential between the substrate 120 and the surrounding medium 185 toreflect light. This antireflective property can be either intentionallywavelength selective or operable across a purposely broad span ofwavelengths. The transition layers 175 can enhance, control, orotherwise manage antireflection (or suppression of optical reflection).

In one exemplary embodiment of the present invention, the optical thinfilm 110 generates or heightens reflectivity in the interface betweenthese two media 120, 185. The thin film structure 175 can enhance,control, or otherwise manage reflection at the material interface 175 orthe outer surface 110.

In one exemplary embodiment of the present invention, the optical thinfilm 110 functions in a bidirectional manner, providing essentiallyequal manipulation of light 125 traveling in either a positive directionor a negative direction with respect to the z-axis 130. That is, thelight 125 can travel through the optical thin film 110 either from theouter surface 185 to the inner surface 170 or from the inner surface 170to the outer surface 185.

The optical thin film 110 in the exemplary optical system 100illustrated in FIGS. 1A and 1B adheres to a substrate 120 that maycomprise a plate of optical material, such as glass, silica, sapphire,or silicon. In this configuration, supporting and stabilizing theoptical thin film 110 is the primary function of the substrate 120,rather than manipulating light such as collimating, beam steering, orfocusing light.

In another exemplary embodiment of the present invention, the substrate120 is a component, such as a gradient index lens or an optical fiber,that provides light manipulation, such as collimating light or guidinglight. Exemplary passive components that can be substrates includediffractive elements, holographic lenses, concave lenses, convex lenses,cylindrical lenses, Fresnel lens, PLCs, prisms, circulators, isolators,lens arrays, ball lenses, micro-optic components, nano-optic elements,planar micro-lens arrays, ion-exchanged components, displays,interconnects, crystals, lenslets, lenticulars, diffusers, micro-fluidiccomponents, or other passive components known to those skilled in theart, according to exemplary embodiments of the present invention.

In addition to passive manipulation, the substrate 120 can activelymanipulate light. That is, the substrate 120 can be part of a verticalcavity surface emitting laser (“VCSEL”), distributed feedback (“DFB”)laser, SOA, silicon optical amplifier (“SiOA”), silicon photonic device,silicon-based laser, Raman laser, erbium doped fiber amplifier (“EDFA”),erbium doped waveguide amplifier (“EDWA”), charge coupled device(“CCD”), light emitting diode (“LED”), avalanche photodiode (“APD”),indium gallium arsenide (“InGaAs”) detector, optical modulator,germanium detector, sensor, or other active component known thoseskilled in the art, in accordance with exemplary embodiments of thepresent invention. The transition layers 175 can enhance operation ofsuch devices.

In one exemplary embodiment, the optical thin film 110 is grown on thesubstrate 120, for example using a fabrication process similar to onethat may be used for fabricating semiconductor devices. In one exemplaryembodiment, the system 100 comprises a semiconductor material, such as asilicon-based material, InGaAs, germanium, indium phosphide, etc., andthe thin film 110 comprises a doped semiconductor. Thus, the thin film110 and the substrate 120 can comprise a monolithic material with thethin film 110 and the substrate 120 having differing levels of a dopant.Alternatively, the thin film 110 and the substrate 120 can each comprisea distinct doping material. The transition layers 175 can be formed withstriations of such doping materials.

In one exemplary embodiment of the present invention, light may travelin the optical thin film 110 along the plane of the optical thin film110, rather than through the thickness 160 of the optical thin film 110as illustrated in FIG. 1. That is, light can either propagate throughthe optical thin film 110 at an acute angle with respect to the z-axis130, parallel to the z-axis 130, or through the optical thin film 110generally parallel to the plane defined by the x-axis 140 and the y-axis150. In one exemplary embodiment of the present invention, the opticalthin film 140 waveguides light. In one exemplary embodiment of thepresent invention, the optical thin film 140 is etched, for example inan inductively coupled plasma (“ICP”) process, to form a structure thatwaveguides light. This waveguide structure can provide single mode lightpropagation.

The thickness 160 of the optical thin film 110 can be of an appropriatedimension to support single mode propagation in the direction of thex-axis 140 or the y-axis 150. In this case, the thickness 160 can berelated to the wavelength of the single mode light and the refractiveindex differential between the optical thin film 110 and the surroundingmaterials 120, 185, which can function as waveguide cladding. Thesedesign parameters may be manipulated by one skilled in the art havingthe benefit of this disclosure to generate specific optical effects, forexample. In one exemplary embodiment, the thickness 160 of the opticalthin film 110 is approximately nine microns, and the mode field of thesingle mode light guided there through is approximately ten microns fora wavelength in the range of approximately 1310 to 1550 nanometers(“nm”). In certain exemplary embodiments, the optical thin film 110 canbe characterized as a relatively thick layer.

In one exemplary embodiment of the present invention, a silicon photonicdevice comprises the optical film 110. The film 110, which may be thin,thick, or of arbitrary thickness, and the silicon photonic device can bea monolithic structure or a unitary structure or multiple structuresfastened, attached, or bonded to one another. In such an embodiment, thefilm 110 can either conduct light though one or both of its faces 170,180 or between/along those faces 170, 180 in a waveguide manner asdiscussed above. The silicon photonic device can comprise a lasingdevice that comprises silicon, an SiOA, a silicon-based modulator, anattenuator comprising silicon, a silicon-based detector, a silicon-basedemitter, and/or an optically-pumped silicon amplifying device, to name afew examples.

Manipulating light at the optical interface of such an active silicondevice via the transition layers 175 can enhance, control, or otherwisemanage an operational aspect of a silicon photonic device. The resultcan be to manipulate or change the optical function, performance, orcharacteristics of the active silicon device, for example adjusting itto comply with a performance specification.

The eight documents listed immediately below disclose exemplary siliconphotonic devices that can comprise an optical film or layer, such as theoptical film 110, whose optical properties can be adjusted, managed,enhanced, or controlled using the technology, methods, processes,teachings, or technology discussed herein. That is, according toexemplary embodiments of the present invention, the optical propertiesof the optical films, materials, or elements of the systems disclosed inthe below eight documents can be managed to provide a performanceenhancement or an operational control. Moreover, the films disclosed inthose eight documents can be adapted via the addition of transitionlayers 175. Further, extremely thin film layers that provide lightmanagement at an optical interface can be added to or integrated withthe devices disclosed in those documents. In one exemplary embodiment aprocess, as discussed in further detail below, imparts such a siliconphotonic device with a layer of graphene, graphite, or graphiticmaterial. Such a layer can enhance the silicon photonic device'soptical, electrical, and/or thermal/heat-dissipation performance, forexample. The disclosures of the following eight documents are herebyincorporated by reference:

1) “A Continuous-Wave Raman Silicon Laser,” by Haisheng Rong, RichardJones, Ansheng Liu, Oded Cohen, Dani Hak, Alexander Fang, and MarioPaniccia, Nature 3346, Mar. 2, 2005. Available at www.nature.com/natureand at www.intel.com.

2) “An All-Silicon Raman Laser,” by Haisheng Rong, Ansheng Liu, RichardJones, Oded Cohen, Dani Hak, Remus Nicolaescu, Alexander Fang, and MarioPaniccia, Nature, Volume 433, Jan. 20, 2005. Available atwww.nature.com/nature and at www.intel.com.

3) “Silicon Shines On,” by Jerome Faist, Nature Volume 433, Feb. 17,2005. Available at www.nature.com/nature and at www.intel.com.

4) “Continuous Silicon Laser, Intel researchers create the firstcontinuous silicon laser based on the Raman effect using standard CMOStechnology,” by Sean Koehl, Victor Krutul, and Mario Paniccia, publishedby Intel Corporation as a white paper, 2005. Available at www.intel.com.

5) “Intel's Research in Silicon Photonics Could Bring High-speed OpticalCommunications to Silicon,” by Mario Paniccia, Victor Krutul, and SeanKoehl, published by Intel Corporation as a white paper, February 2004.Available at www.intel.com.

6) “Silicon Photonics,” by Mike Salib, Ling Liao, Richard Jones, MikeMorse, Ansheng Liu, Dean Samara-Rubio, Drew Alduino, and Mario Paniccia,Intel Technology Journal, Volume 08, Issue 02, May 10, 2004. Availableat www.intel.com (http://developer.intel.com/technology/itj/index.html).

7) “Introducing Intel's Advances in Silicon Photonics,” by MarioPaniccia, Victor Krutul, Sean Koehl, published by Intel Corporation as awhite paper, February 2004. Available at www.intel.com.

8) “Intel Unveils Silicon Photonics Breakthrough: High-Speed SiliconModulation,” by Mario Paniccia, Victor Krutul, and Sean Koehl,Technology@Intel Magazine, February/March 2004. Available atwww.intel.com.

Referring now to FIG. 1B, the optical thin film 110 can be operative tomanipulate light 125 of various or highly selective wavelengths regions.In one exemplary embodiment of the present invention, the optical thinfilm 110 manipulates visible light 125 between about 400 nm and about700 nm. In one exemplary embodiment of the present invention, theoptical thin film 110 manipulates light 125 in the near infrared regionbetween about 700 nm and about 3500 nm. In one exemplary embodiment ofthe present invention, the optical thin film 110 manipulates lightbetween about 700 nm and about 900 nm. In one exemplary embodiment ofthe present invention, the optical thin film 110 manipulates UV light125. In one exemplary embodiment of the present invention, the opticalthin film 110 manipulates light 125 at typical single-mode opticalnetworking wavelengths, in the region between about 1200 nm and about1750 nm. In one exemplary embodiment of the present invention, theoptical thin film 110 manipulates light 125 in one or more spectralregions that provide low-loss transmission over optical fibers. Suchlow-loss spectral regions can be windows of low water absorption, suchas about 1310 nm and about 1550 nm. The thickness 160 of the opticalthin film 110 can be selected to provide specific manipulation effectsof light 125 or electromagnetic radiation.

In one exemplary embodiment of the present invention, the optical thinfilm 110 is an element in a sensor system and is operative to guidelight in a direction generally parallel to the x-y plane 140, 150. Theouter surface 180 of the optical thin film 110 provides a sensinginterface. Light propagating in the optical thin film 110 interacts withthe medium 185 that is adjacent this sensing interface.

In one exemplary embodiment of the present invention, the optical thinfilm 110 and/or the transition layers 175 are formed in a depositionprocess, which can be ion plating, ion assisted deposition (“IAD”), ionsputtering, plasma assisted deposition, or magnetron sputtering. Ionplating can be carried out with evaporation and/or with plasma. Thedeposition process can be a vacuum process, conducted in a depositionchamber at a pressure of less than one atmosphere. These depositionprocesses can be reactive, for example reactive ion beam sputtering.Introducing nitrogen gas into the deposition chamber while sputteringsilicon dioxide can form a transition layers 175 of silicon oxynitridein a reactive manner. Alternatively, a silicon target can be sputteredwhile introducing oxygen and nitrogen into the deposition chamber.

In one exemplary embodiment of the present invention, a physical vapordeposition (“PVD”) process such as evaporation or sputtering forms theoptical thin film 110 and/or the transition layers 175. In one exemplaryembodiment of the present invention, electron-beam (“e-beam”)evaporation or dual e-beam evaporation forms the transition layers 175and/or the optical thin film 110. In one exemplary embodiment of thepresent invention, e-beam IAD beam ion assisted deposition forms thetransition layers 175 and/or the optical thin film 110. Reactive e-beamIAD can form the transition layers 175 and/or the optical thin film 110by introducing nitrogen into the deposition chamber during e-beam IADusing a silicon dioxide target in a reactive process that can be astoichiometric process.

In one exemplary embodiment of the present invention, direct current(“DC”) sputtering or radio frequency (“RF”) sputtering forms thetransition layers 175 and/or the optical thin film 110. The sputteringprocess can be carried out in a reactive manner, for example. Thetransition layers 175 and/or the optical thin film 110 can also beformed with pulsed laser deposition. The optical thin film 110 and/orthe transition layers 175 can also be printed or spun on to thesubstrate 120 or formed with a sol gel process.

In one exemplary embodiment of the present invention, the transitionlayers 175 and/or the optical thin film 110 are formed with epitaxialgrowth, such as liquid phase epitaxy (“LPE”), molecular beam epitaxy(“MBE”), vapor phase epitaxy (“VPE”). In one exemplary embodiment of thepresent invention, the optical thin film 110 is formed with a chemicalvapor deposition (“CVD”) process such as atmospheric pressure chemicalvapor deposition (“APCVD”), low-pressure chemical vapor deposition(“LPCVD”), very low-pressure chemical vapor deposition (“VLPCVD”),plasma-enhanced chemical vapor deposition (“PECVD”), laser-enhancedchemical vapor deposition (“LECVD”), metal-organic chemical vapordeposition (“MOCVD”), or electron-cyclotron resonance chemical vapordeposition (“EPCVD”). The above list of processes for forming theoptical thin film 110 and/or the transition layers in accordance withvarious embodiments of the present invention is an exemplary, ratherthan an exhaustive, list.

In one exemplary embodiment of the present invention, the optical thinfilm 110 and the accompanying transition layers 175 are deposited on theoptical substrate 120 in a vacuum deposition process. In anotherexemplary embodiment of the present invention, the optical thin film 110and the accompanying transition layers 175 are grown on a siliconsubstrate. Thus, the substrate 120 is silicon and the material adheringthereto are composed of an oxide layer on the surface of the silicon.

In one exemplary embodiment of the present invention, the transitionlayer 175 and/or the optical thin film layer 110 is composed of siliconoxynitride (SiO_(n)N_(y)) grown by a hybrid deposition based on thecombination of pulsed laser deposition of silicon in an oxygenbackground together with a plasma based nitrogen source. Controlling thepartial pressure of nitrogen with respect to oxygen in the depositionchamber controls the nitrogen content in the optical thin film 110and/or the transition layers 175.

In one exemplary embodiment of the present invention, the transitionlayer 175 and/or the optical thin film 110 is produced by reactivemagnetron sputtering of a silicon target in a variable mixture of oxygenand nitrogen, which are the reactive gasses. The resulting opticalstructures comprise silicon oxynitride (SiO_(x)N_(y)). Adjacentindividual layers (typically nano-scaled) of the transition layers 175can comprise varying concentrations of oxygen and/or nitrogen, whereinthose concentrations control refractive index. Thus, the values of “x”and “y” in the SiO_(x)N_(y) can vary in each layer.

In one exemplary embodiment of the present invention, the transitionlayers 175 and/or the optical thin film 110 comprise amorphous siliconoxynitride with at most a trace level of Ge. Moreover, the fabricationprocess can comprise electron beam physical vapor deposition (“EB-PVD”)at a low temperature.

In one exemplary embodiment of the present invention, the transitionlayers 175 and/or the optical thin film 110 are formed via reactive RFsputter deposition. Sputtering a silicon nitride target in an oxygenenvironment can form the transition layers 175 and/or optical thin film110. Varying the flow rate of oxygen in the deposition chamber cancontrol the refractive indices to form the individual layers of thetransition layers 175, for example providing refractive indices betweenapproximately 1.46 and 2.3. The RF power can be approximately 500 wattsand the refractive index of the deposited material can vary in a linearmanner with respect to the oxygen flow rate. With a sputtering gashaving approximately ten percent (10%) oxygen and ninety percent (90%)argon, adjusting the gas flow rate between approximately nine standardcubic centimeters per minute (“sccm”) and twenty one sccm can produce acorresponding and essentially linear control of refractive index betweenapproximately 1.8 and 1.5.

In one exemplary embodiment of the present invention, the optical thinfilm 110 is an antireflective coating comprising the transition layers175 with a composition of silicon oxynitride generated in an ion-beamsputtering deposition system. Such film 110 can be essentially void ofGe. The optical thin film 110 can further be a stoichiometric layer,formed in a reactive ion-beam sputtering process and having a highdensity and essentially no so-called columnar structures visible inscanning electron microscopy analysis.

The substrate 120 can be a semiconductor material, including asemiconductor laser facet or an optical amplifier facet. Alternatively,the optical thin film 110 can be a high reflectivity coating on a laserfacet, for example on the back facet of a laser die or a semiconductordevice that amplifies light. In both cases the optical thin film 110 cancomprise or be associated with the transition layers 175.

In one exemplary embodiment of the present invention, the optical thinfilm 110 and the accompanying transition layers 175 are formed with aphysical vapor deposition process based on RF sputtering, which caninclude dual frequency RF sputtering. Several options are available tocontrol the refractive index during the deposition process. Adjustingthe deposition temperature can control the refractive index, with anincrease in deposition temperature providing an increase in refractiveindex. Increasing the RF power applied to the target during thedeposition process also can increase refractive index. Adding a reactivegas to the sputtering chamber can modulate the chemical composition ofthe deposited material, thereby imparts the individual transition layers175 with corresponding changes in refractive index. Furthermore, using atarget material in a specific oxidation state can control refractiveindex during the deposition process.

The RF sputtering method is also applicable to depositing pure materialsand mixed materials including rare earth dopants. Adding a reducing gas,such as hydrogen, to the chamber while the optical thin film 110 and theaccompanying transition layers 175 are forming can provide an increasein refractive index. On the other hand, the refractive index can bedecreased by adding an oxidizing gas, such as oxygen. Replacing argon asthe sputtering gas with approximately two percent (2%) hydrogen (H₂) inargon may increase the refractive index by approximately two percent(2%) or more. In one exemplary embodiment of the present invention, aportion of the hydrogen may remain in the system 100 followingdeposition.

Replacing a portion of the argon gas that is present in RF sputteringenvironment with nitrogen can adjust the composition and refractiveindex of the transition layers 175 and the optical thin film 110. Forexample replacing approximately thirty three percent (33%) of such argonwith nitrogen while sputtering a silicon dioxide (SiO₂) target mayyields approximately seven percent (7%) increase in refractive index.Fabricated in this manner, the optical system 100 may containSiO_(x)N_(y).

In one exemplary embodiment of the present invention, such nitrogen isintroduced in the deposition chamber during the formation of a wavedivision (“WDM”) filter, DWDM filter, or course wave divisionmultiplexing (“CWDM”) filter having layers of tantalum pentoxide andsilicon dioxide. Injecting nitrogen into the chamber during thedeposition of one or more silicon dioxide layers, such as a specifictransition layer in a multi-cavity filter can cause those layers tocontain SiO_(x)N_(y). Evacuating the nitrogen from the chamber followingformation of such a layer can reduce the level of SiO_(x)N_(y) insubsequent silicon dioxide layers.

In one exemplary embodiment of the present invention, a silicon monoxide(SiO) target is sputtered in an argon environment to impart one or moreselected transition layers of the transition layers 175 with arefractive index of slightly above 2. Altering the composition of thesputtering environment can lower the refractive index to approximately1.75, for example to produce selected low-refractive index transitionlayers within the transition layer system 175.

Processes that may be used in connection with fabricating the system100, including the transition layers 175 and the thin film layer 110,include: RF sputtering deposition of SiO₂; RF sputtering deposition ofSiO₂ with index modulation; RF sputtering deposition of SiO and erbiumdoped SiO; single and/or dual frequency RF sputter deposition of silica;PECVD deposition, to name a few possibilities.

In one exemplary embodiment of the present invention, the composition ofat least one of the transition layers 175 and/or the optical thin film110 can be represented by the formula Si_(1-x)Ge_(x)O_(2(1-y))N_(1.33y)wherein “x” is approximately between 0.05 to 0.6, and “y” isapproximately between 0.14 and 0.74. The resulting refractive index canbe approximately from 1.6 to 1.8, variable with composition, processconditions of film formation, heat treatment, and other factors. Thesubstrate 120 can be glass, silicon, or another optical oroptoelectronic material.

Such optical thin films 110 and transition layers 175 can be formed witha PECVD process using a parallel plate reactor with a heated stationaryplaten, a low frequency (375 kHz) RF generator and matching network, anda gas manifold supplying silane, germane (germanium hydride, GeH₄),nitrous oxide, ammonia, and nitrogen into the process chamber through ashowerhead nozzle that uniformly distributes the reactive gasses.

In another exemplary embodiment of the present invention, the transitionlayers 175 and/or the optical thin film 110 is formed by mechanicallyprocessing a boule or preform of optical fiber material. Thus, a processfor forming the system 100 can comprise processing a blank or rod of thefiber optic material that might otherwise be drawn into optical fiber ina process conducted in a drawing tower. The stock of fiber opticmaterial can be temporarily attached, for example in a jigconfiguration, to a base substrate and ground down through mechanicalgrinding and polishing. Alternatively, the material can be thinned withchemical, plasma-based, or ion-based etching conducted in a vacuumenvironment or ICP etching.

In one exemplary embodiment, the compensation of the optical thin film110 and/or the transition layers 175 can have a specific concentrationwithin a range of concentrations of Ge—O₂, for example between 0.25percent and 15 percent. In one exemplary embodiment, a section of theoptical thin film 110 and/or at least one of the transition layers 175comprises essentially pure silicon dioxide, with only trace levels ofGe.

In one exemplary embodiment of the present invention, the system 100comprises boron and Ge. For example, the boron may be co-doped withapproximately 12% Ge in SiO₂.

In one exemplary embodiment of the present invention, the thin film 110illustrated in is deposited on the substrate 120 as essentially puresilicon dioxide, which typically includes small quantities of siliconmonoxide and various impurities.

In one exemplary embodiment of the present invention, the system 100comprises a composition of fused silica with a GeO₂ mole-fractionconcentration between 0.12 and 0.16. In one exemplary embodiment of thepresent invention, the system 100 comprises a composition of vacuumdeposited silica with a GeO₂ mole-fraction concentration between 0.02and 0.16. In one exemplary embodiment of the present invention, the GeO₂mole-fraction concentration of at least some portion of the system 100varies from a level that approaches zero to a level of approximately2.0. In one exemplary embodiment of the present invention, the system100 comprises a composition of silicon dioxide with a GeO₂ mole-fractionconcentration greater than 0.04.

In one exemplary embodiment of the present invention, energy can be usedto control or to adjust an optical property of the transition layers175, or of a larger system that comprises the transition layers 175.Exemplary technology, including a method and a system, for controlling,adjusting, or managing such an optical property is provided in U.S.Nonprovisional patent application Ser. No. 11/127,558, filed May 12,2005 and entitled “Adjusting Optical Properties of Optical Thin Films,”the entire contents of which are hereby incorporated herein byreference.

Turning now to FIG. 2, this figure illustrates an exemplary stack ofoptical thin films 175, 220, 230, 240 on a substrate 120 according to anembodiment of the present invention. In various embodiments, the system200 can be characterized as comprising laminated layers or adjoiningfilms of optical material or sections of optical materials facing oneanother. As discussed above with reference to FIG. 1, the system 200 cancomprise transition layers 175, for example at the interfaces 275between the individual thin film layers 220, 230, 240. Exemplaryembodiments of such transition layers 175 will be discussed below infurther detail with reference to FIGS. 4-16.

The optical system 200 can comprise part of a thin film optical filter,such as a dense wavelength division multiplexing (“DWDM”) filter or alaser-rejection filter for laser-Raman spectroscopy. As an opticalfilter, the optical system 200 can be a high pass filter, a low passfilter, a band pass filter, or a notch filter. Alternatively, theoptical system 200 can provide gain compensation, gain flattening,chromatic dispersion compensation, group delay correction, spectrallyselective delay in an optical network or other optical manipulationbased on interference of light interacting with each of the thin filmlayers 175, 220, 230, 240, the interfaces 275 of thin film layers 175,220, 230, 240 and the substrate 120. In one exemplary embodiment of thepresent invention, this optical system 200 is an element in afrequency/wavelength locking system, such as an etalon-based “locker,”for a telecommunication application. One or more of the thin film layers220, 230, 240 in the stack typically has accompanying transition layers175 that enhance the performance of the system 200.

Moreover, an exemplary embodiment of the present invention can includemultiple optical thin film layers 175, 220, 230, 240 individuallyinteracting with light 125 of an end-use application. For example, thelight 125 may have digital information coded thereon, and the lightinteractions from each individual layer 220, 230, 240 are collectivelyadditive or subtractive upon one another.

One or more of the layers 175, 220, 230, 240 can embody certainfunctions described herein and illustrated in the examples,compositions, tables, functional block diagrams, and appended flowcharts. However, it should be apparent that there could be manydifferent ways of implementing aspects of the present invention inoptical films, and the invention should not be construed as limited toany one optical thin film configuration. Further, a skilled engineerwould be able to create various thin film embodiment without difficultybased on the exemplary functional block diagrams, flow charts, andassociated description in the application text, for example.

Therefore, disclosure of additional designs of stacks of the opticalthin film layers 175, 220, 230, 240, beyond those presented herein, arenot considered necessary for an adequate understanding of how to makeand use the present invention. The inventive functionality of anymultilayer aspects of the present invention will be explained in moredetail in the following description in conjunction with the remainingfigures illustrating the functions, compositions, applications, andprocesses. That is, the transition layers 175 can be applied to a widerange of applications including interference filters and other systems.

For many filtering applications, the pass band(s) and the reflectionband(s) of the system 200 should be flat, with a high level oftransmission and minimal or controlled ripple. The system 200 shouldalso provide a minimal level of light rejected within the pass band formany applications. Rejected light, particularly if the optical system200 reflects the rejected light, can cause problems for an application.For example, reflected light within a pass band can mix with thereflected light outside the pass band and become interference or straylight that can degrade the signal-to-noise ratio of an opticalcommunication system, optical instrumentation system, or other opticalsystem. Consequently, a high degree of stray light rejection (or a highlevel of transmission) within the pass band of a thin film opticalfilter is typically desirable. In many circumstances, the transitionlayers 175 can promote isolation, reduce stray light, control ripple, orenhance the flatness of pass bands or reflection bands.

In one exemplary embodiment, the transition layers 175 can control,improve, or reduce optical dispersion or group delay. Whereas groupdelay is typically measured in the units of picoseconds (“ps”),dispersion is typically measured in picoseconds per nanometer (“ps/nm”).That is, dispersion can be the derivative, with respect to nanometers,of group delay.

Improving the dispersion or group delay of the system 200 can enhanceoptical performance in a high-speed optical networking application, forexample an environment of transmitting data at 10 Gigabit per second, 40Gigabits per second, or at a higher rate. For example, a high level ofdispersion or group delay performance can support a desirable bit errorrate performance in an optical communications network. Similarly,improved group delay can relax a laser specification for an opticalnetwork application.

Thus in an exemplary embodiment, the transition layers 175 can controlthe residence times of photons having different colors in an opticaldevice. That is, the transition layers 175 can help a device, such asthe system 200, operate over a span of wavelengths with defined orcontrolled levels of delay for light of those wavelengths.

In one exemplary embodiment of the present invention, the chromaticdispersion characteristics of the transition layers 175 can correct orcompensate for chromatic dispersion. For example, controlling thedispersion or group delay of the system 200 to achieve a desiredspectral profile can be more beneficial than minimizing those opticalcharacteristics.

Moreover, transition layers 175 can manage dispersion or a group delayspectral profile of an optical device to meet a target specification.The resulting device can compensate for chromatic dispersion of opticalsignals occurring on a span of fiber, in an optical amplifier, or lasercavity, for example. Accordingly, the transition layers 175 can controlthe chromatic dispersion of a compensating device so that the device canbe placed in series with other devices that chromatically disperse lightand so that the aggregate chromatic dispersion is flat.

The Thin Film Center Inc. of Tucson Ariz. provides products and servicesthat can be useful in modeling certain aspects of the system 200.Moreover, the company's design and analysis package, marketed under theproduct name “The Complete Macleod” can be a useful tool for designingthe configuration of the layers 175, 220, 230, 240 to achieve aparticular application objective.

The software products of Software Spectra Inc, the Thin Film Center, andother suppliers of analytical tools for optical coatings, can supportmodeling thin film layers, such as the layers 175, 220, 230, 240 of theoptical system 200. Such software can assist a designer in specifyingvarious parameters of the system 200 to achieve a desired opticaleffect. For example, specifying certain parameters could supportachieving a group delay target. Yet another useful coating design andanalysis tool is the software product known under the trade nameFILMSTAR and available from FTG Software Associates of Princeton, N.J.

The above discussion, with reference to FIG. 1, of embodimentvariations, forms, uses, fabrication processes, applications, etc.generally applies to the system 200 of FIG. 2. For example, the system200 might comprise a monolithically integrated or crystallinesemiconductor material having compositional striations that functionallyform the layers 175, 220, 230, 240. Thus, the layers 220, 230, 240 canarise from variations (or spatial modulations) in one or more dopingchemicals (or elements) of an otherwise homogenous material.Nevertheless, the following discussion with will concentrate on anexemplary embodiment of thin film layers 220, 230, 240, that maycomprise oxide or dielectric material, adhering to an optical substrate120 as might be formed in a vacuum deposition chamber.

Accordingly, the thin film layers 175, 220, 230, 240 can be deposited onthe substrate 120 in a vacuum or near-vacuum deposition process. Thesubstrate can be glass, BK-7 glass, silicate, fused silica, silicon, orother optical material that is generally transparent to or that isotherwise compatible with the wavelengths of the light (exemplaryillustrated as the element 125 in FIG. 1) that the optical system 200manipulates.

The stack includes thin film layers 175, 220, 230 of alternatingrefractive index disposed face-to-face or adjacent one another. Thus,the layers denoted with the reference number “220” may be highrefractive index, while the layers denoted with the reference number“230” may be relatively low refractive index. In one exemplaryembodiment of the present invention, the material compositions of thehigh refractive index layers 220 and the low refractive index layers 230(and/or the transition layer 175) include tantalum pentoxide (Ta₂O₅) andsilicon dioxide (SiO₂) respectively.

In one exemplary embodiment of the present invention, the composition ofat least one of the layers 175, 220, 230, 240 includes siliconoxynitride. In one exemplary embodiment of the present invention, thecomposition of at least one of the thin film layers 175, 220, 230, 240includes diamond (such as diamond-like carbon), graphene, graphiclayers, graphitic material, magnesium fluoride (MgF₂), dielectricmaterial, silicon, titanium dioxide (TiO₂), aluminum oxide (Al₂O₃),metal oxide, among other possibilities.

In one exemplary embodiment of the present invention, the composition ofat least one of the thin film layers 175, 220, 230, 240 includesgermanium (Ge). In one exemplary embodiment of the present invention, atleast one of the alternating refractive index thin film layers 175, 220,230, 240 is an essentially pure optical material. The packing density ofthe alternating refractive index layers 175, 220, 230, 240 is typicallygreater than 95 percent. The physical properties of these layers 175,220, 230, 240 typically approach that of bulk material.

The exemplary stack of optical thin film layers 175, 220, 230, 240includes two spacer layers 240, that may function to provide amulti-cavity interference device. Thus, the system 200 of thin films cancomprise a plurality of cavities that function as an etalon. The spacerlayers 240 are each disposed between two banks 250 of layers 175, 220,230 of alternating, high-low refractive index material. In one exemplaryembodiment of the present invention, the composition of one or more ofthe spacer layers 240 includes silicon dioxide or another dielectricmaterial. In one exemplary embodiment of the present invention, thecomposition of one or more of the spacer layers 240 includes siliconoxynitride. In one exemplary embodiment of the present invention, thecomposition of one or more of the spacer layers 240 includes germaniumand/or hydrogen. In one exemplary embodiment of the present invention,each of the spacer layers 240 is deposited as an essentially pureoptical material. The packing density of the spacer layers 240 istypically greater than 95 percent. The physical properties of theselayers 240 approach that of bulk material.

The transition layers 175 can be graduated along the x-axis 140 so thatvarious ones of the transition layers 175 are different from one anotherin some aspect. Thus, a transition layer 175 at a first location alongthe x-axis 140 can be different (for example in form, composition, orfunction) from a transition layer 175 at a second location along thex-axis 140. The differences among the transition layers 175 can beprogressive or gradual, for example. Alternatively, the transitionlayers 175 can be essentially uniform with respect to one another alongthe x-axis 140. That is, each of the transition layers 175 can haveessentially the same form, function, composition, or operability alongthe x-axis 140.

In one exemplary embodiment of the present invention, the banks 250 ofhigh-index layers 220 and low-index layers 230 are composed of tantalumpentoxide and silicon dioxide respectively and the transition layers 175comprise silicon oxynitride, tantalum pentaoxide, and/or silicondioxide.

In one exemplary embodiment of the present invention, the high indexlayers 220 are tantalum pentoxide; the low-index layers 230 are composedof magnesium fluoride; and the transition layers 175 comprise siliconoxynitride, magnesium fluoride, tantalum pentoxide, and/or silicondioxide.

The transition layers 175 can enhance the operation or utility of a thinfilm optical filter for example providing precise control over centerwavelength, an improved level of light rejection, or enhancedtransmission.

In one exemplary embodiment of the present invention, the layers 175,220, 230, 240 are formed with e-beam IAD. The high-index layers 220 andlow-index layers 230 are composed of tantalum pentoxide and silicondioxide and are deposited on an optical substrate 120 using tantalumpentoxide and silicon dioxide targets in sequence for each respectivelayer 220, 230. Further, the transition layers 175 comprise tantalumpentoxide and silicon dioxide and are deposited using tantalum pentoxideand silicon dioxide targets in sequence for each respective transitionlayer 175.

In one exemplary fabrication embodiment, when the deposition processprogresses to each transition layer 175, a process controller activatesa silicon dioxide target and adds nitrogen to the deposition chamber atan appropriate level to impart the respective layers of each transitionlayer 175 with a predefined refractive index. The controller canmodulate the silicon dioxide and nitrogen discretely or in controlledsteps, thus forming transition layers 175 or individual transitionlayers that comprise silicon oxynitride.

After forming each set of transition layers 175, the deposition processcan shut off the nitrogen supply, eliminate the nitrogen from thedeposition chamber, and return to depositing silicon dioxide andtantalum pentoxide, with only minimal or trace concentrations ofnitrogen in the high-index layers 220 and low-index layers 230 of thelayer bank 250.

In one exemplary embodiment of the present invention, the system 200 isa thin film optical filter or other multi-layer interference device andis formed by ion beam sputtering. At least one of the layers 175, 220,230, 240, 250 could be formed by dual ion beam sputtering.

In one exemplary embodiment, at least one of the layers 175, 220, 230,240, 250 comprises silicon oxynitride that can be represented asSiO_(x)N_(y), with a refractive index between approximately 1.5 and 2.0,depending on the relative values of “x” and “y.”

In one exemplary embodiment of the present invention, an opticalnetworking device comprises the system 200. For example, an add-dropoptical multiplexing (“OADM”) filtering device can comprise the system200. In this embodiment, the substrate 120 can be a gradient index lenswith the thin film layers 175, 220, 230, 240 operating as a notch filterthat provides a narrow band of reflection.

One ingress single mode optical fiber (not shown) delivers multi-colorlight to the gradient index lens, on the opposite side of lens from thethin film layers 175, 220, 230, 240. The lens, which is typically insidea device housing, collimates this multicolor light from the ingressfiber and delivers the collimated light to the thin film layers 175,220, 230, 240. The reflection band or notch of the filter 200 reflects aspectral region of light, delivering the reflected light as one or moredrop channels to a drop fiber that is adjacent the ingress fiber.Meanwhile, the transmission region of the filter 200 transmits theexpress channels to an egress fiber that is butted to another lens onthe opposite side of the thin film layers 175, 220, 230, 240 from thesubstrate 120 (which is the other grin lens in this example).

An optical network, such as a SONET, gigabit Ethernet, access, storage,local area network (“LAN”), Internet protocol (“IP”), or other networkcan comprise the system 200, functioning as the described OADM filter.Such a network can carry a wide range of voice, data, video, or othercommunications.

As discussed above, the transition layers 175 can enhance performance ofsuch an OADM notch filter, for example helping control a centerwavelength of a stop band, the cut-on wavelength of a stop band, thedispersion, the group delay, or the attenuation profile.

In one exemplary embodiment of the present invention, the system 200comprises a planar graphite, graphene, or graphitic layer. A method andsystem for making such a layer is disclosed in U.S. Pat. No. 7,015,142,entitled “Patterned Thin Film Graphite Devices and Method for MakingSame” and filed on Jun. 3, 2004, the entire contents of which are herebyincorporated herein by reference. Moreover, a graphitic, graphite, orgraphene layer can have an accompanying set of transition layers 175. Inone exemplary embodiment, a plurality of adjoining graphitic, graphite,or graphene layers produces an interference effect on electrons presentin the layers. Accordingly, such layers can filter electrons accordingto wavelength, frequency, or energy level. In one exemplary embodiment,a graphitic, graphite, or graphene layer is patterned with a corrugationor a series of grooves that functions as a grating for electrons movingin the layer. Thus, a graphitic, graphite, or graphene layer fabricatedin accordance with the disclosure of U.S. Pat. No. 7,015,142 can beetched to provide a structure that interacts with electrons viadiffraction or interference.

In one exemplary embodiment of the present invention, the substrate 120is a block, slab, or crystal of silicon, and the thin film layer 110 isa graphitic layer or comprises graphite or graphene. In one exemplaryembodiment, the substrate 120 is such silicon and the thin film layer110 is a single graphene layer, with a single or essentially unitarylayer of carbon atoms. In one exemplary embodiment, the substrate 120 issuch silicon, and the thin film layer 110 is a graphite layer made of aplurality of layers of carbon atoms. The number of layers can becontrolled to an exact or approximate number or to be within a specifiedrange. The film 110 can, for example, have a thickness of two, five,ten, fifteen, twenty, fifty, seventy five, one hundred, or in a rangethereof. Such carbon atoms can be crystalline or otherwise have along-term order, structure, or repeated pattern.

Comprised of graphitic, graphite, or graphene material, the layer 110can be formed on the substrate 120 of silicon by creating a siliconcarbide layer on silicon and then processing the silicon carbide layerto form the graphitic, graphite, or graphene layer. The silicon carbidelayer can be formed on silicon using a technology and/or processdisclosed or taught in U.S. Pat. No. 5,861,346, which is entitled“Process for Forming Silicon Carbide Films and Microcomponents” andissued Jan. 19, 1999 in the name of Hamza et al., the entire contents ofwhich are hereby incorporated herein by reference. The resultingproduct, silicon substrate with silicon carbide attached thereto, can beprocessed using a technology and/or process disclosed or taught in U.S.Pat. No. 7,015,142, which is discussed above. Accordingly, from thesilicon carbide, the processing can create graphite, graphene, orgraphitic material adhering to the silicon substrate. The layerattachment can be direct, without requiring glues or bonding agents, forexample.

In one exemplary embodiment, the silicon substrate can actively processlight or electrons that couple to or from the graphite, graphene, orgraphitic layer. In one exemplary embodiment, light propagating in thesilicon substrate interacts with the graphite, graphene, or graphiticlayer. In one exemplary embodiment, electrons propagating in the siliconsubstrate interact with the graphite, graphene, or graphitic layer. Inone exemplary embodiment, light propagating in the graphite, graphene,or graphitic layer interacts with the silicon substrate. In oneexemplary embodiment, electrons propagating the graphite, graphene, orgraphitic layer interacts with the silicon substrate. In one exemplaryembodiment, light and/or electrons propagating in the silicon substrateinteract light and/or electrons propagating in the graphite, graphene,or graphitic layer.

Accordingly, the graphite, graphene, or graphitic layer can enhance,control, or manage the operation of the system to which it is attached.For example, the silicon substrate can comprise integrated elements,such as transistors or logical gates, that manipulate electrons viapower levels (or some other transistor-type function). And, thegraphite, graphene, or graphitic layer can comprise integrated elements,such as gratings, interferometers, etalons, or thin film stacks, thatmanipulate the electrons via interference or diffraction. The activesubstrate and the layer can function in a collaborative manner, forexample manipulating the same electrons in a serial or parallel manner.

An exemplary processes for fabricating a system comprising graphite,graphene, or graphitic material atomically or molecularly bonded to asilicon base follows below, as Steps A, B, C, D, and E. In one exemplaryembodiment, the process, or a derivative thereof, can produce a siliconphotonic device, as discussed above, that comprises a layer of graphene,graphite, or graphitic material.

At Step A, one or more known silicon processing techniques impartsilicon base with one or more patterns, features, active areas,transistors, gates, light manipulators, amplifiers, optical amplifiers,micro electromechanical systems (“MEMS”) elements, optical devices,lenses, logical elements, doped features or regions, active elements,etc.

At Step B, typically following Step A, processing in accordance with thedisclosure and teaching of U.S. Pat. No. 5,861,346 forms, deposits, orprovides one or more layers of silicon carbide on the silicon substratethat results from Step A.

In one exemplary embodiment, the silicon carbide material can compriseone or more patterns, features, active areas, transistors, gates, lightmanipulators, amplifiers, optical amplifiers, micro electromechanicalsystems (“MEMS”) elements, optical devices, lenses, logical elements,doped features or regions, active elements, etc. An exemplary method ortechnology for forming such an active element in the silicon carbide canbe found in U.S. Pat. No. 6,278,133, entitled “Field Effect Transistorof SiC for High Temperature Application, Use of Such a Transistor, and aMethod for Production Thereof,” the entire contents of which are herebyincorporated herein by reference. Another exemplary method or technologyfor imparting the silicon carbide material with a useful feature ordevice can be found in U.S. Pat. No. 6,127,695, entitled “Lateral FieldEffect Transistor of SiC, a Method for Production Thereof and a Use ofSuch a Transistor,” the entire contents of which are hereby incorporatedherein by reference.

At Step C, typically following Step B, processing in accordance with thedisclosure and teaching of U.S. Pat. No. 7,015,142 forms a layer orlayers of graphite, graphene, or graphitic material using part oressentially all of the silicon carbide film as a precursor, a basematerial, or a stock.

Accordingly, a silicon-carbide-based element (such as one or morepatterns, features, active areas, transistors, gates, lightmanipulators, amplifiers, optical amplifiers, micro electromechanicalsystems (“MEMS”) elements, optical devices, lenses, logical elements,doped features or regions, active elements, etc.) can comprise graphite,graphene, or graphitic material, such as a layer or a film thereof.

At Step D, typically following Step C, processing in accordance withU.S. Pat. No. 7,015,142 imparts a layer or layers of graphite, graphene,or graphitic material with a structure, such as a Mach-Zenderinterferometer, a diffraction grating, a corrugated grating, an etalon,or a stack of layers, that is operative to manipulate electrons viainterference or diffraction.

At Step E, typically following Step D, the resulting system can beplaced in operation. Placing the system in operation typically comprisessupplying the system with light, electrons, or some other form ofenergy. In operation, light, electrons, particles, radiant energy,and/or energy waves couple between the silicon substrate and thelayer(s) that comprises graphite, graphene, or graphitic material.

Turning briefly to FIG. 3, FIGS. 3A and 3B, respectively illustrate across sectional view 325 and a refractive index plot 300 of aconventional stack of optical thin film layers. As discussed above inthe Background, conventional optical thin film systems often have abruptchanges or a “step changes” in refractive index and in materialcomposition at the interfaces 330, 340, 350 between each thin film layer360, 370. In many situations, smoothing such step changes, such asprovided by transition layers 175 (not shown in FIG. 3 but discussedbelow) is desirable.

Turning now to FIG. 4, this figure illustrates a high-level plot 400 ofrefractive index of a plurality of exemplary thin film layers, generallyresembling a smoothed square wave, according to an embodiment of thepresent invention. The plot 400 can also be viewed as a square wave withrounded edges. The plot 400 provides an exemplary result of adapting thesystem 325 of FIG. 3A so that the adapted version of the system 325comprises transition layers 175 at the interfaces 330, 340, 350.

Adding the transition layers 175 can provide the smooth refractive indextransitions 410, 420, 430 of the plot 400 of FIG. 4 in contrast to theabrupt refractive transitions or refractive index discontinuities shownat the places 330, 340, 350 of the plot 300 of FIG. 3.

Thus, the plot 400 of FIG. 4 exemplifies a refractive index profile ofthe layers 220, 230 and the accompanying interfaces 175 and transitionlayers 175 of the system 200 shown in FIG. 2 and discussed above. Thearea (along the horizontal axis) between the marker 410 and the marker420 corresponds to a high index layer 220. Meanwhile, the area betweenthe marker 420 and the marker 430 corresponds to a low index layer 230.And, the marker 420 corresponds to the interface 275 between those twolayers 220, 230.

Further, the plot 400 can provide an exemplary material profile of thesystem 200, where the vertical axis of FIG. 4 represents materialcomposition rather than refractive index.

As will be discussed in further detail below, the refractive indexprofile 400 of FIG. 4 can have additional structures that provides theillustrated smooth curves. For example, the individual layers transitionlayers, while having individual abrupt material and refractive indexchanges, may create an aggregate smoothing effect as shown in FIG. 4.Thus, light propagating in the vicinity of one of the interfaces 275 canexperience the transition layers 175 as a relatively smooth transitionor ramp. In other words, the smooth plot 400 can provide arepresentation of refractive index from the perspective of lightpropagating in the vicinity of an interface 275 that has accompanyingtransition layers 175.

Turning now to FIG. 5, this figure illustrates a high-level plot 500 ofrefractive index of a plurality of exemplary thin film layers 220, 230,175, generally resembling a sinusoidal waveform, according to anembodiment of the present invention. The markers 510 and 520 indicate afull cycle of periodicity of the plot 500 and the material structurethat the plot 500 characterizes. In addition to being representative ofrefractive index (as labeled on the vertical axis of the plot 500), theplot 500 can be representative of a periodic variation of materialcomposition.

In one exemplary embodiment, the plot 500 can be the result of havingtransition layers 175 disposed essentially throughout adjoining highindex and low index layers 220, 230. For example, the system 200 of FIG.2 can be adapted to provide the refractive index profile 500 bydistributing transition layers 175 throughout layers 220, 230, ratherthan concentrating the transition layers 175 at the interfaces 275.

In one exemplary embodiment, the sinusoidal plot (or some similaroscillating profile or periodic waveform) can provide a gratingfunction. For example, imparted with the sinusoidal variation viatransition layers 175, a stack of thin film layers 220, 230 can be orcan comprise an optical transmission or refection grating.

Turning now to FIG. 6, this figure illustrates a refractive index plot600 of a plurality of thin film layers 175, 220, 230, wherein a net oraverage refractive index profile 675 overlays a detail plot 650 thatdepicts the refractive index pattern of a series of exemplary transitionor transitional thin film layers 175 disposed at an interface 275between major thin film layers 220, 230, according to an embodiment ofthe present invention.

In one exemplary embodiment, the plot 600 describes in further detailthe physical structure that underlies the plot 500 of FIG. 5, discussedabove. That is, the thin films 175, 220, 230 that the plot 600 describescan be similar in form, function, or composition, or can share someother attribute, to the thin film embodiment of the plot 500.

In one exemplary embodiment, the profile or plot 675 describesrefractive index from the perspective of light 125 propagating throughthe thin film structure 175, 220, 230. Meanwhile, the profile or plot650 describes refractive index on a nano scale, for example as might beresolved by a very high resolution scanning electron microscope (SEM) orsome other material analyzing system with nano-scale resolution.Alternatively, the profile 650 can describe theoretical refractive indexvariations that may be too small to be analyzed with typical analysisinstruments.

In one exemplary embodiment of the present invention, the profile 675can be viewed as an averaged or a filtered version of the profile 650.The profile 650 can describe the physical characteristics or the actualphysical dimensions of the thin film structure 175, 220, 230. Meanwhile,the profile 675 can describe the net, resultant optical characteristicsor the actual optical performance of that structure, 220, 230.

In one exemplary embodiment, the transition layers 175 that the profile650 describes are sufficiently thin, for example a few atoms thick, suchthat light 125 passing there through may interact with each individuallayer 175 as if those individual layers 175 were smoothly varying ratherthan as bulk material. Thus, the light 125 interacting with theindividual transition layers 175 may interact in a manner distinct fromthe manner in which light interacts with a bulk material that hasdimensions on the order of the wavelength of light.

The portion of the profiles 650, 675 above the marker 610 (on thehorizontal axis) describes an exemplary low index layer 230. Similarly,the portion of the profiles 650, 675 above the marker 630 describesanother exemplary low index layer 230. Thus, the centers of the layers220 typically lie directly over the respective markers 610, 630.Meanwhile, the portion of the profiles 650, 675 above the marker 620describes an exemplary high index layer 220, with the center of thelayer 230 typically lying directly over the marker 620.

The portion of the profiles 650, 675 between the marker 610 and themarker 620 (over the marker 615) describes a transition between a centerof a low refractive index layer 230 and a center of a high refractiveindex layer 220. Similarly, the portion of the profiles 650, 675 betweenthe marker 620 and the marker 630 describes a transition between acenter of a high refractive index layer 220 and a center of a lowrefractive index layer 230. As illustrated, the plot 600 exhibitsexemplary symmetry of the profiles 650, 675 (and the associatedtransition layers 175) around the layer centers.

Between the center of the low refractive index layer 230 (directly overthe marker 610) and the midpoint of the transition (directly over themarker 615), transition layers that have high refractive index aredisposed in that layer 230. As illustrated, those high index transitionlayers have essentially uniform thickness. As further illustrated, theseparation between those high index transition layers decreases movingfrom the center point 610 of the low index layer 230 towards thetransition midpoint 615.

Between the midpoint of the transition (directly over the marker 615)and the center 610 of the high refractive index layer 220 transitionlayers that have low refractive index are disposed in that high indexlayer 220. As illustrated, those low index transition layers haveessentially uniform thickness. As further illustrated, the separationsbetween those individual low index transition layers increases in thedimension moving from the transition midpoint 615 towards the centerpoint 620 of the high index layer 220.

As an alternative to viewing the transition layers as being disposed inor added to high and low index primary layers 220, 230, the system oflayers 175, 220, 230 that FIG. 6 describes can be viewed as a series oflayers of discrete or binary refractive index (and/or materialcomposition) that function in a collaborative manner. The thicknesses ofand separation between the individual layers of that series, while beingindividual abrupt, present the light 125 with a gradual change inrefractive index.

The illustrated portions of the profiles 650, 675, between the marker610 and the marker 630 represent a full cycle of low index and highindex layers 220, 230. While a single cycle is illustrated, the cyclemay repeat, for example as a stack of alternating refractive indexlayers.

In many situations, utility can result from using high index layers 220that have a different thickness than the low index layers 230. Moregenerally, the high index layers 230 and the low index layers 220 canhave respective optical, geometric, or physical thicknesses that may bethe same, similar, essentially equal (for example within manufacturingtolerance), or purposefully different.

Turning now to FIG. 7, this figure illustrates a refractive index plot700 of a plurality of thin film layers 175, 220, 230, wherein a net oraverage refractive index profile 775 overlays a detail plot 750 thatdepicts the refractive index pattern of a series of exemplary transitionor transitional thin film layers 175 disposed at an interface 275between major thin film layers 220, 230, according to an embodiment ofthe present invention. As discussed above, the profile 775 can describerefractive index from the perspective of the light 125, while theprofile 750 can describe refractive index on the nano-scale. Thus, apoint on the profile 750 might describe the refractive index exhibitedby a slab of bulk material having a composition that corresponded tothat point. In other words, the plot 750 can describe the measurablerefractive index of a transition layer, if that transition layer was tenor more wavelengths thick rather than extremely thin. Meanwhile, theprofile 875 can describe the composite, average, or systemic refractiveindex.

Whereas the exemplary embodiment of FIG. 6, discussed above, hastransition layers 175 distributed across, or essentially throughout, thehigh and low index layers 220, 230, the exemplary embodiment of FIG. 6has those transition layers 175 concentrated at the midpoint 715 betweenthe center 710 of the low index layer 230 and the center 720 of the highindex layer 220. Accordingly, the profiles 750, 775 have flat sectionsat the layer centers 710, 720, 730.

The thin film system embodiment of FIG. 7 can be viewed has havingfeathered, sloped, or beveled transitions between the adjoining layers220, 230. Moreover, the plot 700 can describe a device that provides therefractive index profile 400 of FIG. 4, discussed above. That is, theexemplary embodiment of FIG. 7 can be similar to or can correspond tothe exemplary embodiment of FIG. 4, discussed above.

Turning now to FIG. 8, this figure illustrates a refractive index plot800 of a plurality of thin film layers 175, 220, 230, wherein a net oraverage refractive index profile 875 overlays a detail plot 875 thatdepicts the refractive index pattern of a series of exemplary transitionor transitional thin film layers 175 disposed at an interface 275between major thin film layers 220, 230, according to an embodiment ofthe present invention.

In the region between the marker 805 and the marker 820, the plot 800describes a transition between a low index layer 230 and a high indexlayer 220. In the region between the marker 820 and the marker 840, theplot 800 describes a transition between a high index layer 220 and a lowindex layer 230. In some applications or embodiments, a singletransition will be appropriate. Benefit may result from having atransition from a section of high index material that is not necessarilya thin film, to a section of low index material that is not necessarilya thin film.

For example, a core of an optical waveguide might comprise the highindex region 820, and a material surrounding the core, such as acladding, might comprise the low index region 805. In this situation,the transition region 805 can be the boundary or the area between thecore and the cladding. In this manner, the transition layers 175 cansupport an optical effect that is similar to a gradient index fiber or agradient index lens.

In one exemplary embodiment, the high index material may have adifferent phase than the low index material. For example, the high indexmaterial could be a waveguide, a piece of glass, a semiconductor, or apiece of plastic, which the low index material could be water, a liquid,or a gas, such as air. In this situation, the transition layers maycomprise regions of the high index material that lead up to the lowindex material. Thus, the transition layers may function as a lead in,an antireflective structure, or even a high index structure.

In one exemplary embodiment, the transition layers (or another thin filmstructure) may provide a different function or result according to thematerial that is in contact with the high index section at anyparticular time. That result can comprise a change in color,reflectivity, polarization, transmission, absorption, phase, etc. Forexample, a polymer, monofilament, or plastic fishing line can be coatedwith transition layers or another film. The coating can be applied tothe line after it is formed. Alternatively, the polymer line and thecoating can be drawn or extruded from a nozzle or spinneret, for examplein one pass.

The coating can be highly reflective when the fishing line is in an airenvironment. Meanwhile, when the coated fishing line is in contact withwater, the reflection can disappear or be suppressed. That is, atransition layer or another coating can provide high reflectivity orvisibility for the portion of the line that is above a lake and canprovide low reflectivity, low visibility, or high transparency for theportion of the line that is in the lake. Moreover, the perceived colorof the line can change based on whether it is immersed in water. In thismanner, the fishing line can be visible or colorful to the fisherman andessentially invisible to the fish.

Referring now to FIG. 8, the refractive indices of the transition layers175 are modulated in a manner that manages the light 125 that ispropagating in the vicinity of the interface 275 or boundary between thehigh index layer 220 and the low index layer 230. Moreover, thetransition layers 175 can provide a lead-in, a tapered transition, aharmonizing effect, or a soft surface to the light 125. In one exemplaryembodiment, the transition layers 175 cushion the light waves or thephotons as they move between the high index layer 220 and the low indexlayer 230. In one exemplary embodiment, the transition layers 175 canrefract the light incident thereon.

As illustrated, at least some of the individual layers of the transitionlayers 175 can be uniformly spaced with respect to one another. That is,some or essentially all of individual layers above the marker 810 can beequally spaced or disposed as if on a grid. The distance (geometric oroptical) between the first transition layer and the second transitionlayer can be essentially equal to the distance between the secondtransition layer and the third transition layer, etc. The thicknesses ofeach of those individual layers of the series can vary gradually so thatthe net amount of material is graduated in a discrete manner across theinterface 175, 810. That is, the transition layers 175 can comprise asystem of progressively thicker and/or thinner layers. And, thetransition layers 175 can comprise a system of successively thickerand/or thinner layers. Those individual layers can be substantiallythinner than the wavelength of managed light 125 that is incidentthereon. In one exemplary embodiment, those individual layers can besubstantially thinner than one-fourth the wavelength of the managedlight 125.

An equation that describes the progressive change in thickness can behyperbolic, sinusoidal, exponential, linear, or decaying exponential,for example. Rather than conforming to a particular equation, theprogressive change can follow a computer-generated specification,profile, or equation. For example, an optical simulation softwareprogram can generate a set of coordinates or target values that adeposition process can meet via intermittently depositing two or morematerials.

The individual transition layers can exhibit symmetry on one side of theinterface 275, 810 relative to the other side of the interface 275, 810.Alternatively, the transition layers 175 can be asymmetric with respectto the interface 275, 810. In one exemplary embodiment, the transitionlayers 175 associated with the marker 810 can be different (in number,thickness, geometry, functionality, etc.) than the transition layers 175associated with the marker 830.

The optical system that the plot 800 describes can also be viewed as alow refractive index material into which high refractive index layershave been disposed. Starting at the left side of the plot 800, thosehigh index layers are progressively thicker towards the marker 820.Thus, the amount of high index material increases gradually in discretesteps from the marker 805 to the marker 820 and then decreases from themarker 820 to the marker 840. The relative amounts of the high indexmaterial and the low index material can be viewed as having a gradient,a gradual slope, or a graduated character. Moreover, the transitionlayers 175 can impart the system with a blended composition of opticalmaterials without necessarily mixing those materials in a uniform orhomogeneous manner. Thus, a system of extremely thin layers can behaveoptically like a system of mixed optical materials.

Turning now to FIG. 9, this figure illustrates a refractive index plot900 of a plurality of thin film layers 175, 220, 230, wherein a net oraverage refractive index profile 975 overlays a detail plot 950 thatdepicts the refractive index pattern of a series of exemplary transitionor transitional thin film layers 175 disposed at an interface 275between major thin film layers 220, 230, according to an embodiment ofthe present invention. In an exemplary embodiment, the profile 975 canbe characterized as the composite effect of the individual transitionalstructures that the plot 950 details.

The plot 900 generally describes a system having two section of highrefractive index material, respectively associated with the markers 910and 930, that bracket a section of low refractive index material,associated with the marker 920. The transition layers 175 provide acontrolled material transition between the high refractive indexmaterials and the low refractive index materials. As illustrated, thelow index section is thicker than the high index sections. In oneexemplary embodiment, the low index section, associated with the marker920 emits light or otherwise comprises an active light source. In oneexemplary embodiment, at least one of the high index sections,associated with the markers 910, 930, emits light or otherwise comprisesan active light source. In one exemplary embodiment, each of thesections 910, 920, 930 functionally manages at least one of light andelectrons.

Cross sectional illustrations of exemplary systems of transition layerswill be discussed below with reference to FIGS. 10-14. The exemplaryembodiments of FIGS. 10-14 can generally correspond to the exemplaryembodiments of FIGS. 6-9. That is, FIGS. 10-14 provide additionalinformation, in the form of representative cross sectional views, aboutsystems that FIGS. 6-9 describe graphically, in the form of plots orprofiles.

Turning now to FIG. 10, this figure illustrates a cross sectionalprofile of an exemplary plurality of thin film layers 1000 that managelight 125 at an interface 275/275 a between two optical materialsections 220 a, 230 a according to an embodiment of the presentinvention. The two optical material sections 220 a, 230 a can beexemplary embodiment of the layers 220, 230 discussed above.Accordingly, the system 1000 illustrates an exemplary embodiment ofplurality of transition layers 175 as discussed above. Moreover, thesystem 1000 can correspond to one of the plots 600, 700, 800, 900discussed above.

In an exemplary embodiment of the system 1000, the layers 220 a, 1015,1014, 1013, 1012, 1011, 1010 comprise material having relatively highrefractive index, and the layers 230 a, 1020, 1021, 1022, 1023, 1024,1025 comprise material having relatively low refractive index. In oneexemplary embodiment, the layers 220 a, 1015, 1014, 1013, 1012, 1011,1010 have a common composition. In one exemplary embodiment, the layers1015, 1014, 1013, 1012, 1011, 1010 have a common composition that isdistinct from the composition of the layer 220 a. In one exemplaryembodiment, the layers 230 a, 1020, 1021, 1022, 1023, 1024 have a commoncomposition. In one exemplary embodiment, the layers 1020, 1021, 1022,1023, 1024 have a common composition that is distinct from thecomposition of the layer 230 a. The materials of each of the layers1020, 1021, 1022, 1023, 1024 and the layers 1015, 1014, 1013, 1012,1011, 1010 are typically, but not necessarily completely, homogeneous orhave essentially uniform internal structures.

In the illustrated exemplary embodiment, the layers 1025, 1024, 1023,1022, 1021, 1020 have similar or essentially the same thickness 1075.The layers 1015, 1014, 1013, 1012, 1011, 1010 have progressively lessthickness 1050. That is, the layers 1015, 1014, 1013, 1012, 1011, 1010decrease in thickness from the layer 220 a towards the layer 230 a. Thedecrease can be linear, decaying exponential, exponential, geometric,etc. or follow some other equation or computer-generated formula orpattern.

In one exemplary embodiment, the dimension 1021 can be less than 10nanometers. In one exemplary embodiment, the dimension 1021 can be in arange of 10 to 25 nanometers. In one exemplary embodiment, the dimension1021 can be in a range of 1 to 5 nanometers. In one exemplaryembodiment, the dimension 1021 can be approximately 50 to 100nanometers.

In one exemplary embodiment, the dimension 1021 can be less thanapproximately one-tenth the wavelength of the light 125 that the system1000 is operative to manage. In one exemplary embodiment, the dimension1021 can be less than approximately one-fiftieth the wavelength of thelight 125 that the system 1000 is operative to manage. In one exemplaryembodiment, the dimension 1021 can be less than approximately one-fourththe wavelength of the light 125 that the system 1000 is operative tomanage. In one exemplary embodiment, the dimension 1021 can be less thanapproximately one-twentieth the wavelength of the light 125 that thesystem 1000 is operative to manage. In one exemplary embodiment, thedimension 1021 can be less than approximately one percent of thewavelength of the light 125 that the system 1000 is operative to manage.In one exemplary embodiment, the dimension 1021 of at least one of thelayers 1025, 1024, 1023, 1022, 1021, 1020 can be less than approximately0.1% or 0.01% of the wavelength of the light 125 that the system 1000manages.

In one exemplary embodiment, the dimensions 1050 of the layers 1015,1014, 1013, 1012, 1011, 1010 can progress from about 1000 nanometers toabout 5 nanometers. In one exemplary embodiment, the dimensions 1050 ofthe layers 1015, 1014, 1013, 1012, 1011, 1010 can progress from about100 nanometers to about 1 nanometers. In one exemplary embodiment, thedimensions 1050 of the layers 1015, 1014, 1013, 1012, 1011, 1010 canprogress from about 500 nanometers to about 3 nanometers. In oneexemplary embodiment, the dimensions 1050 of the layers 1015, 1014,1013, 1012, 1011, 1010 can progress from about 100 nanometers to about 2nanometers.

In one exemplary embodiment, the dimensions 1050 of the layers 1015,1014, 1013, 1012, 1011, 1010 can progress from about one-fourth to aboutone-hundredth of the wavelength of the light 125 that the system 1000 isoperative to manage. In one exemplary embodiment, the dimensions 1050 ofthe layers 1015, 1014, 1013, 1012, 1011, 1010 can progress from aboutone-tenth to about one-hundredth of the wavelength of the light 125 thatthe system 1000 is operative to manage. In one exemplary embodiment, thedimensions 1050 of the layers 1015, 1014, 1013, 1012, 1011, 1010 canprogress from about one-tenth to about one-thousandth of the wavelengthof the light 125 that the system 1000 is operative to manage. In oneexemplary embodiment, the dimensions 1050 of the layers 1015, 1014,1013, 1012, 1011, 1010 can progress from about one-tenth to aboutone-thousandth of the wavelength of the light 125 that the system 1000is operative to manage.

While the illustrated number of layers of the exemplary system 1000 isrelatively small, other embodiments may comprise many more layers, forexample twenty-five, fifty, one hundred, one thousand, or more.

Turning now to FIG. 11, this figure illustrates a cross sectionalprofile of an exemplary plurality of thin film layers 1100 that managelight 125 at an interface 275/275 b between two optical materialsections 220 b, 230 b according to an embodiment of the presentinvention. Accordingly, FIG. 11 illustrates an exemplary embodiment of aplurality of transition layers 175, in the form of the system 1100. Thematerial sections 220 b, 230 b can be exemplary embodiments of thematerials 220, 230 discussed above.

The layers 1125, 1124, 1123, 1122, 1121, 1120 each comprises materialhaving relatively low refractive index, for example as measured in bulkform. Meanwhile, the interleaved or interspersed layers 1115, 1114,1113, 1112, 1111, 1110 have contrasting refractive indices, for examplerelatively high refractive indices.

From the material section or layer 220 b towards the material section orlayer 230 b, the layers 1125, 1124, 1123, 1122, 1121, 1120 haveprogressively increasing thicknesses 1121. From the layer 230 b towardsthe material section 220 b, the layers 1110, 1111, 1112, 1113, 1114,1115 have progressively increasingly thicknesses 1150. Thus, the averagerefractive index of the system 1100 gradually changes between the layer220 b and the layer 230 b. The individual layers 1125, 1124, 1123, 1122,1121, 1120, 1110, 1111, 1112, 1113, 1114, 1115 that contribute to therefractive index profile can be viewed as providing a terrace or alattice of refractive index and/or composition.

As discussed above with respect to FIG. 10, the layers 1125, 1124, 1123,1122, 1121, 1120, 1110, 1111, 1112, 1113, 1114, 1115 typically havenano-scale features and dimensions 1121, 1114.

Turning now to FIG. 12, this figure illustrates a cross sectionalprofile of an exemplary plurality of thin film layers 1200 that managelight 125 at an interface 275 c between two optical material sections230 c, 220 c in accordance with an exemplary embodiment of the presentinvention. The interface 275 c provides an exemplary embodiment of theinterface 275 that is discussed above. The illustrated material sections220 c, 230 c provide exemplary embodiments of the materials 220, 230that are discussed above.

The layers 1260 and the layers 1280 have essentially the same materialcomposition as the layer 230 c. And, the layers 1270 and the layers 1290have essentially the same material composition as the layer 220 c. Eachof the layers 1260 have similar thicknesses 1230, and each of the layers1290 have similar thicknesses 1220. As discussed above, those thicknessdimensions 1230, 1220 are typically very small, even on the scale oflight. In one exemplary embodiment, the dimensions 1230, 1220 are smallenough to avoid any individual layer 1290, 1270 creating substantialoptical interference impacting the operable spectral region of thesystem 1200.

The axis 1210 is associated with or is aligned to the interface 275 cand illustrates an approximate midpoint or centerline of the transitionlayer system 1200. From the section 220 c to the axis 275 c, therespective thicknesses 1235 of the series of the layers 1270, which areinterleaved between the layers 1260, successively decreases. From thesection 230 c to the axis 275 c, the respective thicknesses 1225 of theseries of the layers 1280, which are interleaved between the layers1290, successively decreases.

The varying thicknesses 1225 of the layers 1280 can be similar to thevarying thicknesses 1235 of the layers 1270. Accordingly, the system1200 can have a type of symmetry on the upper side 1240 of the referenceline 1210 relative to the lower side 1250. The two variations can serveto provide a balanced lead-in to the axis 1210 and a correspondinglead-out from the axis 1210.

Turning now to FIG. 13, this figure illustrates a cross sectionalprofile of an exemplary plurality of thin film layers 1300 that managelight 125 at an interface 275 d between two optical material sections220 d, 230 d according to an embodiment of the present invention. Theinterface 275 d and the optical material sections 220 d, 230 d of FIG.13 can respectively be exemplary embodiments of the interface 275 andthe optical materials sections 220, 230 discussed above.

The system 1300 comprises a section 1340 above the reference line 1310,which is shown at a nominal or arbitrary location of the materialinterface 275 d and a section 1350 below the reference line 1310.Geometrically, the sections 1340, 1350 can generally be symmetrical withrespect to one another (with appropriate material substitutions).Accordingly, the lower section 1350 is labeled with reference numeralsand will now be discussed.

The section 1350 comprises a series of layers 1360 that lead up to (orform part of) the interface 275 d, providing a transition from thematerial section 220 d towards the material section 230 d. The layers1360 are typically made of the same material as the section 230 d. Thematerial between each of the layers 1360 typically has the samecomposition as the material of the section 220 d.

The density or number of the layers 1360 increases towards the line1310. That is, there are a greater number of layers towards theinterface line 1310 than towards the material section 220 d. Morespecifically, in the illustrated exemplary embodiment, the section 1325comprises one of the layers 1360. The section 1326 comprises two of thelayers 1360. The section 1327 comprises three of the layers 1360. Thesection 1328 comprises four of the layers 1360. The sections 1325, 1326,1327, 1328 may have similar optical or geometric thicknesses, forexample each being 5, 10, 20, 30, 40, or 50 nanometers thick, or in arange thereof. The layers 1360 can have a thickness of about 1, 2, 3, 5,7, 10, or 15 nanometers, or in a range thereof. These dimensions cancorrespond to managing light 125 of about 500, 750, 1000, 1250, or 1550nanometers and can be linearly scaled up or down for other wavelengths,for example.

Turning now to FIG. 14, this figure illustrates a cross sectionalprofile of an exemplary plurality of thin film layers 1400 that managelight 125 at an interface 275 e between two optical material sections220 e, 230 e according to an embodiment of the present invention. Theinterface 275 e and the material sections 220 e, 230 e can compriserespective exemplary embodiments of the interface 275 and the materialsections 220, 230 discussed above.

Between the high index section 220 e and the low index section 230 e aredisposed an arrangement of high index layers 1460, and low index layers1470 that are operative to manage light transmission in the vicinity ofthe interface 275 e. The imaginary line 1410 (not physically present ina operating device) represents a somewhat arbitrary location of theinterface 275 e, for illustrative purposes. The section 1440 and thesection 1450 exhibit symmetry about the line 1410, with a between thesections 1440, 1450 distinction being that the compositions of thelayers are reversed or swapped, as shown in the cross sectional view ofFIG. 14.

The layers 1470 progressively increase in thickness from the materialsection 220 e towards the line 1410, and further increase in thicknesstowards the material section 230 e. Meanwhile, the layers 1460progressively decrease in thickness from the material section 220 etowards the line 1410, and further decrease in thickness towards thematerial section 230 e.

In one exemplary embodiment, the successive decrease in the sizes of thelayers 1460 from the material section 230 e to the material section 220e parallels or directly corresponds to the successive decrease in thesizes of the layers 1470 from the material section 220 e to the materialsection 230 e. Those layers 1460, 1470 can vary across the interface 275e from about one-fourth to about one-hundredth or about one-thousandththe center wavelength of the managed light 125. In one exemplaryembodiment, the layers 1460, 1470 can vary from about 300 nanometers toabout 10 nanometers, or from about 250 nanometers to about 5 nanometers,between the sections 220 e and 230 e. In one exemplary embodiment, thelayers 1460, 1470 can vary across the system 1400 from about one atom inthickness to a thickness that behaves similar to bulk material.Moreover, the layers can have a thickness of atoms that varies fromabout 2 to about 100, from about 5 to about 1000, from about 10 to about10,000, from about 50 to about 100,000, from about 1-10 to about1,000-100,000-1,000,000, or in some range thereof, for example. Invarious exemplary embodiments, those variations can occur over a seriesof 25, 50, 100, 250, or 500 of the layers 1460, 1470.

An exemplary process for fabricating an optical system comprising astructure for managing light 125 at an optical interface 275 and anexemplary process for managing light 125 via such a fabricated structurewill be discussed below with reference to FIGS. 15 and 16. In certainembodiments, one or more of those processes, or other processesdisclosed or taught herein, may comprise or involve computer programs,computer-implemented steps, or software.

Accordingly, some exemplary embodiments the present invention caninclude multiple computer programs embodying certain functions describedherein and illustrated in the examples, functional block diagrams, andappended flow charts. However, it should be apparent that there could bemany different ways of implementing aspects of the present invention incomputer programming, and the invention should not be construed aslimited to any one set of computer program instructions. Further, askilled programmer would be able to write such computer programs withoutdifficulty based on the exemplary functional block diagrams, flowcharts, and associated description in the application text, for example.

Therefore, disclosure of a particular set of program code instructionsis not considered necessary for an adequate understanding of how to makeand use the present invention. The inventive functionality of anyprogramming aspects of the present invention will be explained in moredetail in the following description in conjunction with the remainingfigures illustrating the functions and program flow and processes.

Certain steps in the processes described below must naturally precedeothers for the present invention to function as described. However, thepresent invention is not limited to the order of the steps described ifsuch order or sequence does not alter the functionality of the presentinvention. That is, it is recognized that some steps may be performedbefore or after other steps or in parallel with other steps withoutdeparting from the scope and spirit of the present invention.

Turning now to FIG. 15, this figure illustrates a flowchart of anexemplary process 1500 for fabricating optical components that comprisea series of thin film layers that manage light 125 at an interface 275between two optical material sections 220, 230 according to anembodiment of the present invention. While Process 1500, which isentitled Fabricate Component Comprising Index Transition, could beapplied (directly or via adaptation) to multiple of the exemplaryembodiments discussed herein, for illustrative purposes, reference willprimarily be made to the system 1100 of FIG. 11 (discussed above) andthe system 200 of FIG. 2 (also discussed above).

At Step 1510, a loading apparatus places a substrate 120 (not explicitlyillustrated in FIG. 11) into the thin film deposition chamber. Theloading apparatus can be a robot, a pick-and-place system, or aprogrammable arm, for example. A pump typically evacuates the chamber toa specified vacuum level, leaving at least some gaseous matter in thechamber.

At Step 1515, a deposition source emits high-energy particles ofhigh-refractive index material, such as Ta₂O₅. The particles can be orcan comprise atoms or molecules. In one exemplary embodiment, tantalumparticles emitted from a tantalum source form Ta₂O₅ in the chamber,somewhere between the source and the substrate or at the substrate. Inthis case, the chamber can contain at least some gaseous oxygen thatreacts with the tantalum.

The emitted particles adhere to the substrate 120 and accumulate to forma high index layer 220 b. Feedback from an optical and/or apiezoelectric monitor in the chamber stops the deposition when the layer220 b achieves a sufficient thickness. The target thickness, which couldbe an optical thickness, an absolute thickness, a physical thickness, ora geometric thickness, can be derived from a computer-generated recipefor a thin film interference filter, for example. That is, acomputer-based controller stops deposition when the layer 220 b grows toa specified dimension.

At Step 1520, a deposition source in the chamber begins emittinghigh-energy particles of relatively low refractive index material, suchas SiO₂. As discussed above, the source can comprise silicon dioxide oressentially pure silicon that reacts with oxygen to form silicondioxide. Silicon dioxide adheres to the layer 220 b and accumulates toform the layer 1125. The computer-based controller stops the depositionof silicon dioxide when feedback indicates that the layer 1125 hasachieved sufficient thickness, for example a structure that has aboutten atoms of silicon in a layer cross section.

At Step 1525, the deposition source begins emitting high-energyparticles of Ta₂O₅. With the emission of SiO₂ suspended, the Ta₂O₅accumulates to form the layer 1115, which adheres to the layer 1125 thatformed at Step 1520. The controller suspends deposition of Ta₂O₅ whenfeedback indicates that the layer 1115 has grown to a specifiedthickness. That thickness specification can be in accordance with acomputer-generated recipe or model, for example.

At inquiry Step 1530, the controller determines whether the transitionlayers have formed. For example, the controller determines whether eachof the layers 1125, 1115, 1124, 1114, 1123, 1113, 1122, 1112, 1121,1111, 1120, 1110 have formed according to the recipe. Process 1500iterates Steps 1520 and 1525 until fabrication of those layers iscomplete. In other words, the controller repeats Steps 1520 and 1525 foreach pair of high index and low index layers until the depositionchamber creates each transition layer.

As discussed above, the first iteration of Steps 1520 and 1525 formslayers 1125 and 1115. The second iteration forms layers 1124 and 1114.The third iteration forms layers 1123 and 1113. The fourth iterationforms layers 1122 and 1112. The fifth iteration forms layers 1121 and1111. The sixth iteration forms layers 1120 and 1110. At each iteration,the thickness of the respective high index layer decreases while thethickness of the respective low index layer increases. The iterationsmay continue until 25, 50, or 100 pairs of transition layers haveformed, for example.

Process 1500 executes Step 1535 (via a positive determination at inquiryStep 1530) in response to completing the formation of the layer 1110. AtStep 1535, the deposition source emits particles of low index SiO₂ toform the layer 230 b. The layer 230 b typically is a counterpart to thelayer 220 b. For example, the layers 230 b and 220 b can cooperate toproduce optical interference of the light 125 that the system 1100 isoperative to manage (or constructive and destructive interaction betweenlight waves).

At inquiry Step 1540, the controller determines whether formation of theentire stack 200 (shown in FIG. 2, discussed above) is complete. Asdiscussed above, formation of the stack may follow a computer-generatedrecipe or design specification. If formation of the stack 200 is notcomplete, Process 1500 loops to Step 1515 to iterate Steps 1515, 1520,1525, 1530, 1535, and 1540 until the deposition chamber has formed thestack 200.

When the stack 200 has completely formed, Step 1550 follows Step 1540.At Step 1540, the loading apparatus removes the completed assembly 200from the deposition chamber for deployment in an application. Process1500 ends following Step 1550.

As discussed above, a completed embodiment of the optical system 200,typically comprising multiple instances of the system 1100, may bedeployed to benefit any of various applications. Those applicationsmight include Raman spectroscopy, endoscopes, medical devices, opticalnetworking modules, optical communication systems, flat panel displays,monofilament line, tissue analysis, cut jewels, diamonds, or laserreflectors, to name but a few examples.

Turning now to FIG. 16, this figure illustrates a flowchart of anexemplary process 1600 for using a series of thin film layers to managelight 125 at an interface 275 between two optical material sections 220,230 according to an embodiment of the present invention. Process 1600,which is entitled Manage Light, will be discussed below with exemplaryreference to FIG. 11, such reference being for illustrative purposesrather than as a limitation.

At Step 1610, light 125 propagates in the material section 230 b towardsthe interface 275 b or the adjacent material section 220 b. The light125 can comprise a DWDM signal, an optical packet, Raman-scatteredlight, an emission from a display pixel, amplified light from a siliconphotonic device, etc. As discussed above, the material sections 220 band 230 b have distinct material compositions and refractive indices.

At Step 1620, the light 125 is incident on or upon the layers 1110,1120, 1111, 1121, 1112, 1122, 1113, 1123, 1114, 1124, 1115, 1125. Asdiscussed above, those layers 1110, 1120, 1111, 1121, 1112, 1122, 1113,1123, 1114, 1124, 1115, 1125 typically have alternating refractive indexand composition, with each being essentially homogeneous.

At Step 1630, the light 125 propagates through or otherwise interactswith the layers 1110, 1120, 1111, 1121, 1112, 1122, 1113, 1123, 1114,1124, 1115, 1125, for example in succession. The layers smooth,facilitate, or otherwise manage the transmission of the light 125between the material section 230 b and the material section 220 b.

At Step 1640, the managed light 125 passes into the material section 220b. The managed light, transmitted therein, can have controlledreflection, polarization, spectral content, dispersion, delay, color,etc. Following Step 1640, Process 1600 ends.

Exemplary systems that may benefit from comprising transition layers 175and methods that may benefit from comprising steps for managing light atan optical interface 275 will be discussed below with reference to FIGS.17 through 29.

Turning now to FIGS. 17A and 17B, these figures respectively illustratea representative perspective view and a functional block diagram of anexemplary system 1700 for receiving light 1750 with a detector 1725,wherein the system 1700 adjusts the detector 1725 in advance ofreceiving the light 1750 according to an embodiment of the presentinvention.

Dynamically configurable optical networks, such as DWDM networks thatchange transmission colors and/or routes, can be prone to delivering anunexpected change in light intensity to a receiving system 1700. If theintensity abruptly increases, some conventional receivers can becomesaturated, “blinded,” temporarily impaired, or even permanently damaged.If the intensity abruptly decreases, some conventional receivers cansuffer a bit error, for example failing to properly detect at least someaspect of the incoming signal. The self-adjusting or self-adaptationcapability of the receiver system 1700 can help address or alleviatethis issue.

The receiver system 1700 comprises an optical fiber 1715 that isconnected to a network (not explicitly illustrated in FIG. 17), such asa SONET, Ethernet, FTTH, metro, access, DWDM, CWDM, opticallyreconfigurable, or LAN network. The optical fiber 1715 is connected to aplanar lightguide circuit (“PLC”) 1705 that is connected in turn to adetecting system 1725. The detecting system 1725 is typically anintegrated circuit (“IC”) device, such as an IC chip or a monolithicelement. As an alternative to the PLC 1705, the system 1700 can compriseloops of fiber with a tap or a splitter or an optical delay system, forexample.

In one exemplary embodiment, the PLC 1750 is or comprises a siliconoptical amplifier or some other silicon-based integrated optical device.A silicon optical amplifier can output a signal that is correlated withthe intensity of the traveling wave of light that is propagating in theamplifier. That output signal can feed into a detector that is coupledto the output of the silicon optical amplifier. More specifically, theoutput signal can adjust the detector in advance of the detectorreceiving the traveling wave of light, thereby enhancing the detector'sperformance in receiving that light.

In one exemplary embodiment, an imaging system (not illustrated) cantrouble shoot the PLC 1750. A Raman imaging spectrometer can acquire anoverhead image of the PLC 1750 while light transmits through the PLCwaveguide core. The acquired image can help diagnosis any problems withthe PLC 1750, in any the various embodiments discussed herein, forexample. A problem or flaw in the waveguide core shows up on the image,as one or more intense pixels on the spectrometer's CCD, for example.Kaiser Optical Systems of Ann Arbor, Mich. is a supplier of highsensitivity imaging cameras and spectrometers.

The optical fiber 1715 emits light (typically encoded withcommunications data) into the PLC's waveguide core 1710. The waveguidecore has a z-shaped configuration that operates to release a sampleportion 1745 of the communications light to the detecting system 1725and to direct the remaining portion 1750 of the light to the detectingsystem 1725 after a time delay. During the time delay, the detectingsystem 1725 self adjusts or adapts in preparation for receiving the mainor remaining light 1750. Through the self adjustment, the detectingsystem 1725 can increase or decrease its sensitivity or take measures toavoid damage from an abrupt increase in intensity.

The input face 1720 of the PLC 1705 can have transition layers 175adjacent the optical fiber 1715 to facilitate the transfer of lightbetween the fiber 1715 and the PLC 1705. The transition layers 175 canenhance coupling between a glass fiber and a silicon-based PLC, such asone of the silicon photonic devices discussed above. Light propagatestowards the PLC output face 1745. A sample 1745 of the incident lightpasses through the face 1745 for receipt by the control detector 1735.The face 1745 typically has a partially-reflecting thin film mirror,which may comprise a transition layer, that transmits about 1-5 percentof the incident light as the sample light 1745 and reflects 95-99percent of the incident light.

The reflected light (which will become the main or remaining light 1750)propagates back to the opposite face 1720 of the PLC. A mirror coating(for example a dielectric or a metal mirror) on the opposite face 1720reflects the remaining light 1750 back towards the output face 1750. Theoutput face 1750 transmits the remaining light 1750 to the main detector1730. The output face 1750 may comprise transition layers (notillustrated in FIG. 17 at that interface 1750) to facilitate the lighttransfer.

Accordingly, the control detector 1735 receives the sample light 1745ahead of the main detector 1730 receiving the remaining light 1750. Morespecifically, an optoelectronic/opto-electric detecting region 1761 ofthe control detector 1735 receives the sample light 1745. Some timelater, an optoelectronic/opto-electric detecting region 1762 of the maindetector 1730 receives the main light 1750.

The signal processing module 1765 processes and amplifies the electricalsignal that the region 1761 outputs in response to the sample light1745. Thus, the control detector 1735 outputs an electrical signal thathas an intensity that is related to or that is proportional to theintensity of the sample light 1745. The control module 1752 comprises acomparator 1755 that compares the electrical signal from the controldetector 1735 to a reference signal 1775, which may comprise a voltageand/or a current.

If the signal from the control detector 1735 has greater intensity ormagnitude than the reference signal 1775, the comparator 1755 outputs acontrol signal to the sensitivity control 1770 of the main detector1730. The control signal may be binary or discrete or may alternativelyhave a range of values that indicate or convey the relative strength ofthe sample light 1745.

In response to the control signal from the comparator 1755, thesensitivity control module 1770 adjusts, adapts, or manages theoptoelectronic/electro-optic region 1762 and the signal processingmodule 1765. For example, the sensitivity control module 1770 can tunethe gain of the signal processing module. As another example, thesensitivity control module 1770 can apply a bias or a drain to theregion 1762 based on input from the control module 1752.

Accordingly, the control detector 1735 receives sample light from lightpulses and the main detector 1730 responds to the control signals fromthe control module 1752 in advance of the main detector 1730 receivingthose light pulses. Thus, the main detector 1730 can receive opticalpulses with high fidelity and can decode data from those pulses withhigh reliability.

Turning now to FIG. 18, this figure illustrates a representativeperspective view of an exemplary system 1800 for receiving light,wherein the level of received light is adjusted in advance of receivingthe light according to an embodiment of the present invention.Accordingly, the system 1800 can be characterized as an exemplaryembodiment of a receiver that self adjusts in advance of receiving alight pulse to better receive the light pulse.

Similar to the system 1700 illustrated in FIG. 17 and discussed above,the system 1800 can benefit from having transition layers 175 thatmanage the transfer of light at the interface between the detectingsystem 1725 and the PLC 1705 and/or the interface between the PLC 1705and the optical fiber 1715.

The system 1800 comprises an optical attenuator 1810 that attenuates thelight flowing in the PLC 1705 in response to control signals from thecontrol detector 1735 of the detecting system 1725. The control detector1735 receives sample light 1745 and controls the attenuator 1810 basedon the strength of the sample light 1745. If the sample light 1745 isrelatively intense, the attenuator 1810 attenuates the incoming lightpulses in advance of detection by the main detector 1730. If the samplelight 1745 is relatively weak, the attenuator 1810 allows a largeportion of those light pulses to pass to the main detector 1730.

In an exemplary embodiment, the attenuator 1810 comprise a waveguidecladding with a controllable refractive index. Varying the refractiveindex sets the amount of light that leaks out of the cladding, thusproviding controlled attenuation.

In one exemplary embodiment, the control detector 1735 and the module1752 can determine and model the rate of change of the incoming samplelight 1745, for example as a decaying exponential function or atime-constant response. The detecting system 1725 can control the maindetector 1730 and/or the attenuator 1810 based on modeled change tocompensate for the change. In other words, the system 1800 or the system1700 can operate like a Smith predictor to make predictive changes thatcompensate for delay and time-constant dynamics. That is, the system1800 can change the sensitivity of the main detector 1730 at a rate thattracks and compensators for the rate of change of the incoming opticalsignals before the main detector 1730 receives those optical signal.

Turning now to FIG. 19, this figure illustrates a timing diagram 1900 ofan exemplary system 1700 for receiving light 1750 with a detector 1762,wherein the system 1700 adjusts the detector's sensitivity in advance ofreceiving the light 1750 according to an embodiment of the presentinvention. The timing diagram 1900 is discussed with exemplary referenceto the system 1700 of FIG. 17, discussed above.

At time T1 1905, a light pulse or an optical packet enters an opticalnetworking module, such as a receiver, transceiver, or an optical adddrop multiplexing terminal device.

At time T2 1910, the control detector 1735 receives a sample 1745 of thelight pulse and converts that sample 1745 into the electrical domain.

At time T3 1915, the control circuit 1752 issues control signals oradjustment commands to the main detector 1730 based on the intensity ofthe sample 1745.

At time T4 1920, the main detector 1730 responds to the control signalsfrom the control circuit 1752. The response can be a change insensitivity, gain, etc.

At time T5 1920, the main detector 1730 receives the optical pulses thatcontrol detector 1735 sampled at time T2 1910.

Turning now to FIG. 20, this figure illustrates a flowchart of anexemplary process 2000 for adjusting an optical detector 1730, based onan intensity of an optical signal, in advance of the detector 1730receiving the optical signal according to an embodiment of the presentinvention. Process 2000, which is entitled Control Detector, will bediscussed with exemplary reference to the system 1700 of FIG. 17,discussed above.

At Step 2005, the optical fiber 1715 emits light towards the input facetor face 1720 of the PLC 1720. At Step 2010, the emitted light transmitsthrough the input face 1720 and into the first leg 1720 or a firstsection of waveguide core of the PLC 1705. At Step 2015, the first leg1720 guides the light to an output face 1745, or a sample port, a tap,or a splitter, of the PLC 1720.

At Step 2020, the output facet 1745 transmits a sample portion 1745 ofthe light, such as 0.02 to 3 percent. The control detector 1735 receivesthat sample light 1745. The output facet 1745 directs the remaininglight 1750 to a second leg of the PLC 1720. The light direction can beaccomplished with a thin film reflector or an optical filter that cancomprise a series of transition layers 175, as discussed above.

At Step 2025, the control detector 1735 generates an electrical signalthat carries information about the intensity of the sample light 1745that is incident thereon. In other words, the control detector 1735converts the sample light 1745 from the optical domain to the electricaldomain.

At Step 2030, the control module 1752, which can be viewed as a controlcircuit, compares the generated electrical signal to a reference 1775.At inquiry Step 2035, the control module 1752 determines whether thegenerated electrical signal is greater than the reference signal 1775,for example as a threshold test.

If the generated electrical signal exceeds the reference signal, thenStep 2040 follows Step 2035. At Step 2040, the control module 1755 setsthe main detector 1730 for maximum or heightened gain.

On the other hand, if the generated electrical signal does not exceedthe reference signal, then Process 2000 executes Step 2045 followingStep 2035. At Step 2045, the control module 1755 sets the main detector1730 for reduced sensitivity. In one exemplary embodiment, the controlmodule 1755 takes some other form of corrective action. Such action caninclude diverting light, attenuating light, blocking the main detector1730 with a shutter, obscuring a portion of the remaining light 1759with a variable diameter aperture, moving a MEMS element that controllight, to name a few examples.

A time period elapses between the time that the light sample 1745transmits through the face 1745 and the time that the main detector 1730responds to the control signal from the control module 1752.

Following the execution of Step 2040 or Step 2045, as determined byinquiry Step 2035, Process 2000 executes Step 2050. At Step 2050, thesecond leg guides the remaining light 1750 to a reflector at the PLCface 1720. The second leg and the first leg may be “folded” with respecton one another. That reflector directs the light back to a third leg,which is folded with respect to the second leg. The third leg carriesthe remaining light 1750 back to the output facet 740. The remaininglight 1750 passes through the output facet 740 towards the main detector1730.

The zigzagged or folded first, second, and third legs can have asufficient length to provide an adequate optical delay. In variousexemplary embodiments, the legs can be 10 millimeters, 10 centimeters,or 100 centimeters in length, for example. In one exemplary embodiment,the PLC 1705 can have 10, 50, or 100 folded legs, rather than theexemplary number of three legs shown in FIG. 17. In one exemplary, thePLC 1705 is a backplane of a communications system or a signal buss.

At Step 2055, the main detector 1730 receives and responds to theremaining light 1750, thereby producing an electrical signal thatcorresponds to the intensity of that light 1750. Associated signalprocessing circuitry 1765, typically in concert with external circuitry,decodes information from the remaining light 1750. That informationmight comprise video signals, voice, data, etc.

At Step 2060, a second time period elapses between the point in timethat the PLC output facet 1745 transmits the sample light 1745 and thepoint in time that the main detector 1730 receives the remaining light1750. The second time period is longer than the first time perioddiscussed above. Accordingly, the main detector 1730 is adapted orprepared for receipt of the remaining light 1750 in advance of actuallyreceiving that light 1750.

At Step 2005, the execution of Process 2000 loops back to Step 2005,thereby iterating Steps 2005 through 2065. The iterations provideregular or essentially continuous updates to the receptioncharacteristics of the main detector 1730.

Another exemplary method for receiving an optical signal can proceed inaccordance with the following steps: (a) determining whether an opticalsignal has an intensity greater than a threshold in response toreceiving a first portion of the optical signal at a first detector; and(b) if the intensity of the optical signal is determined to be greaterthan the threshold, adjusting a second detector for receipt of a secondportion of the optical signal in advance of the second detectorreceiving the second portion.

Another exemplary method for receiving an optical signal can proceed inaccordance with the following steps: (a) receiving a first portion of anoptical signal at a first detector at a first time; (b) receiving asecond portion of the optical signal at a second detector at a secondtime, after the first time; (c) determining whether the received firstportion of the optical signal has an intensity that meets a threshold;and (d) if a determination is made that the received first portion ofthe optical signal has an intensity that meets the threshold, sending analert for receipt at the second detector before arrival of the secondportion of the optical signal at the second detector.

Another exemplary method for receiving an optical signal can comprise:(a) transmitting the optical signal into a watertight enclosure of aFTTH system at a premises; (b) monitoring whether the transmittedoptical signal has changed in intensity as compared to a previouslymonitored intensity; (c) if the optical signal has changed in intensityadjusting a detector, within the enclosure, for receipt of thetransmitted optical signal in advance the detector receiving thetransmitted optical signal; and (d) receiving the optical signal withthe adjusted detector.

Turning now to FIGS. 21A, 21B, and 21C, these figures illustrate agemstone prior to 2150 and after 2100 applying an exemplary opticalcoating to a facet 2125, wherein the coating 2125 suppresses facetreflection 2165 according to an embodiment of the present invention. Thecoating 2125 can be or can comprise one or more transition layers 175.The coating 2125 manages the incident light 2105 at the interfacebetween the gemstone 2100 and the surrounding medium, typically air.

A conventional gemstone, such as a conventional cut and uncoated diamond2150, interacts with light 2105 via reflection 2165 and dispersion 2180.As a result of the large difference in refractive index between diamondand air, a large portion of incident light 2105 reflects 2165. Atglancing angles, the fraction of reflecting light 2165 can beparticularly high. The remaining light 2170 enters the diamond 2150 andis refracted by the diamond-air interface. The transmitted light 2170internally reflects from the cut areas 2175 of the diamond 2150 andexits the upper facets, typically above the “girdle” or at the tablefacet. When the light 2180 exits, the light separates into a spectrum ofcolors, in a prismatic effect. The property of the diamond to separatelight into colors in this manner can be referred to as the diamond's“fire.” Oftentimes, diamonds that produce high levels of fire aredesirable. However, the relatively large amount of light 2165 that isreflected prior to entering the diamond 2150 can limit the fire that thediamond 2150 yields.

Explained another way, an uncoated diamond 2150 reflects 2165 most ofthe light 2105 that is incident upon its table facet 2160. Theremaining, un-reflected light 2170 enters the diamond 2150 and bouncesaround within the diamond 2150 and exits the diamond 2150 as multiplecolors 2180, which may appear red, blue, yellow, green, etc. to anobserver. Since a relatively little amount of light 2170 enters thediamond 2150, the intensity of those colors is relatively low. In otherwords, the reflection 2165 limits the intensity of the diamond's fire2180.

In contrast, for the coated diamond 2100, the coating 2125 allows alarger portion 2120 of the incident light 2105 to penetrate the tablefacet 2125. That penetrated light 2120 reflects from within the internalsurfaces 2175 and emerges as intense fire 2130. In other words, thecoated diamond 2100 transmits most of the incident light 2105 andinternally reflects that transmitted light 2120 towards the facets nearthe table facet 2125. The internally reflected light 2120 exits thediamond 2100 and disperses chromatically, or separates into visiblydistinct colors 2130 that are more intense than the colored light 2180of the uncoated diamond 2150. Thus, the coated diamond 2100 producesvivid or intense colors.

The coating 2125 can comprise an antireflective coating, a series oftransition layers, a partially reflective coating, a motheye structure,or an “omnidirectional” filter, for example. Moreover, the transitionlayers can enhance the performance of an omnidirectional filter, anomnidirectional interference device, or an omnidirectionalantireflective coating. Further, the coating can manage, control, orfacilitate transmission of the incident light 2105.

The coating 2125 can be applied selectively to the table facet 2125, toother facets above the girdle or adjacent the table facet 2125, to allthe facets above the girdle, or to the entire gemstone 2100, which canbe a diamond, a cubic zirconium, a sapphire, a ruby, or some otherjewel, for example. A cut gemstone can be masked and placed in adeposition chamber, for example.

Turning now to FIG. 22, this figure illustrates a flowchart of anexemplary process 2200 for using a thin film coating 2125 to suppressreflections 2115 from a facet 2125 of a gemstone 2100 and to enhance thegemstone's fire 2130 according to an embodiment of the presentinvention. Process 2200, which is entitled Enhance Fire, will bediscussed with exemplary reference to FIG. 21C, discussed above.

At Step 2210, a deposition process applies a thin film antireflectivecoating to one or more facets or surfaces of a gemstone, jewel, ordiamond 2100. A masking jig limits the coating deposition to a selectedarea, such as the table facet 2125. The thin film coating typicallycomprises one or more transition layers, as discussed above.Alternatively, the thin film coating may be a single layer of magnesiumfluoride, for example. In some embodiments, the thin film coating maycomprise organic material or polymers that can be removed with asolvent. Such removal can be desirable for some users who may want totemporarily use, test, or experiment with the coating, for examplewithout risking permanent change to their jewelry.

At Step 2220, light rays 2105 propagate towards the coated table facet2125 and are incident thereon. The coating 2125 generates opticalinterference that controls or suppresses light reflection 2115. At Step2230, a relatively large percentage, such as 80%, 85%, 90%, 95%, 98%,99% or in a range thereof, of the incident light 2105 passes through thetable facet 2125 and into the diamond 2100.

At Step 2240, internal surfaces 2175 of the diamond 2100 reflect thelight 2120 that has passed through the table facet 2125. That internallyreflected light 2120 is directed back up towards the table facet 2125and/or the adjacent facets.

At Step 2250, the internally reflected light 2120 exits the facets andis dispersed or separated into a spectrum of colors or vibrant colorpatterns 2130. The diamond 2100 has increased fire or color separationcharacteristics in response to the coating 2125. Following Step 2250,Process 2200 ends.

Turning now to FIG. 23, this figure illustrates an exemplary system2300, comprising a series of apertures 2325, having progressivelyincreasing diameter, that perform a mode expansion on light emitted froman optical fiber 2305 according to an embodiment of the presentinvention. The system 2300 can use diffraction to adiabatically expand asingle mode of light from a single mode fiber, a crystal fiber, or aholey fiber, for example.

The optical fiber 2305 can comprise a core 2310 and a coating 2305 thatincludes series of transition layers 175 adjacent the fiber's end faceto manage light at the optical interface between the fiber 2305 and thesurrounding medium, typically air or some other gas.

The system 2300 comprises a series of plates 2320, membranes, members,films, layers, or some other structures with controlled spacing therebetween. Each plate 2320 has a thickness 2300 and comprises a hole 2325that can be viewed as an aperture or a light port, for example. Thethickness 2330 can be a ratio of the light flowing therein, for example.That ratio can be two fold, one fold, three-fourth, one-half,one-fourth, one-eighth, one-tenth, or in a range thereof, for example.

The holes 2325 have successively or progressively larger diameters. Thediameters near the optical fiber can be about 10 microns or some otherdimension that approximates the diameter of the fiber core 2310. Thediameters 2325 can expand to about 20, 30, 40, or 50 microns or a factorof 1.5, 2, 2.5, or 3 times the core diameter. The system 2300 cancomprise from 5 to about 50 plates 2320, for example.

The plates 2320 can have equal spacing 2335 that is related to thewavelength of the light. For example, the spacing 2325 can be provide aphase relationship. In other words, the plate-to-plate separation 2325can help the plates provide a phased array of apertures 2325 thatgradually expand a single-mode beam of light without unduly breaking thebeam into two or more modes. The total length of the array of plates2320 can be about 20 to 500 microns. The plates 2320 can be parallel toone another or slightly skewed to provide gradual curvature that bends,curves, slightly redirects the beam.

As an alternative to having air between each plate 2320, in oneexemplary embodiment, the plates 2320 can be thin film layers that areintegrally attached to one another. That is, the array of plates 2320can comprise a stack of thin film layers with selected layers having apatterned metallic or other coating that has an aperture that functionsas the hoe 2325. In other words, a solid structure of spaced apertures2325 can function in a similar manner to the system 2300. More over,such as system can be bidirectional, to compress the mode or to expandthe mode with little loss in intensity during the compression orexpansion.

An embodiment of a stack of layers can be fabricated by depositing afirst layer of transparent optical material. The first layer is thenmasked, for example with photolithography. A thin metallic layer is thendeposited to form an opaque layer with an aperture 2325 corresponding tothe masked area. Subsequent layers of transparent material and metal aredeposited on top of the first layer. The thicknesses of the depositedlayers are controlled to provide the distances 2325. The masked areasare controlled to provide progressively larger apertures 2325. In oneexemplary embodiment, the stack also comprises an interference filter.That is, a stack of layers can comprise some layers that filter lightvia interference, some layers that expand the light beam, and/or somelayers that both expand the light beam and filter light.

In one exemplary embodiment, the array of progressively larger aperturesis implemented in a silicon system, such as a silicon photonic device ora silicon optical amplifier. In such embodiment, silicon or some othercrystal can be grown or processed to provide the light-managingapertures 2325.

The system 2300 is typically enclosed in a sealed housing, such as ahermetic enclosure that also encloses a DWDM or CWDM laser, a FTTHreceiver, a transceiver, a filter, or a detector, for example. In oneexemplary embodiment the system 2300 and the system 1700, discussedabove with reference to FIG. 17, are housed in a common opticalnetworking module.

In one exemplary embodiment, the system 2300 processes light forcoupling to an optical filter, for example one of the filtering devicesor system discussed above. In particular, a thin film optical filter canbe disposed adjacent the largest port 2325, so that the filter receivesexpanded-mode light, thereby providing enhanced filtering performance.That is, the system 2300 can present a filter with an expanded lightbeam to promote filtering. As discussed above, in one exemplaryembodiment, the filter and the beam expansion system 2300 are anintegrated or unitary system of thin film layers.

Turning now to FIG. 24, this figure illustrates a flowchart of anexemplary process 2400 for expanding a single mode light beam usingdiffraction associated with a series of progressively larger apertures2325 according to an embodiment of the present invention.

At Step 2400 of Process 2400, which is entitled Expand Mode, a singemode optical fiber 2305 transmits single mode light towards a fiber endface coated with an antireflective film 2315 or a system of transmissionlayers that manage light as discussed above. In one exemplaryembodiment, a PLC, an optical amplifier, a semiconductor laser, or anoptical waveguide transmits the light towards the system 2300.

At Step 2420, the optical fiber end face 2315 (or a tip of anotherwaveguide) emits the single mode light, for example in a transceiver, atransmitter, or a receiver at a home premises. At Step 2430, the singlemode light propagates through the apertures 2325 in a series of parallelplates 2320 or some other structures, as discussed above for example.The apertures 2325 have progressively increasing diameters along thelight path.

At Step 2440, the apertures 2325, typically the peripheries or edges ofthe apertures, diffract the light or otherwise interact with the lightvia a wave-based phenomenon. At Step 2450, the diffraction helps thelight beam expand while the majority of the light energy retains asingle mode format.

At Step 2460, the expanded mode is incident on and is filtered by a thinfilm notch or band pass filter that may comprise transition layers 175as discussed above. Following Step 2460, Process 2400 ends.

Turning now to FIG. 25, this figure illustrates an exemplary surgicalsystem 2500 for cutting biological tissue by applying a light absorber2580 and laser light 2575 to the tissue according to an embodiment ofthe present invention.

In many situations, conventional lasers that offer desirableenergy-delivery characteristics deliver that energy at opticalwavelengths that may fail to interact desirably with tissue. That is, alaser that would otherwise be well suited for surgical applications mayoutput a color or wavelength that is ill suited to interacting withtissue.

For example, certain ultraviolet or visible lasers output light that isabsorbed near or essentially at the tissue surface, with littleuncontrolled penetration, in a manner that is desirable. However, thepower characteristics of those lasers is often insufficient or is lessthan optimal. Thus, many convention ultraviolet or visible lasers offerlimited performance for surgical applications.

On the other hand, while many conventional infrared lasers provide highpower and/or delivery characteristics, the infrared light interacts withtissue over a greater depth or through a larger volume. Accordingly,conventional infrared lasers that can provide suboptimal light-tissuecharacteristics may be limited in the ability to target a surface layerof tissue.

The system 2500, illustrated in FIG. 25, can address this situation byadapting the tissue to enhance the manner in which the light 2575interacts with the tissue or the manner in which the tissue responses tothe light 2575. More specifically, the system 2500 can apply a localizedink 2580, a dye, a chemical, a light absorber, a moiety, an opaquesolution, or another material that helps or induces the interactionbetween the light 2575 and the tissue. The laser light 2575 is incidentupon the localized ink 2580 that has been applied to the tissue surface,and that ink 2580 rapidly absorbs the light 2575. The rapid absorptiontriggers a cascade or a chain reaction whereby the surface of the tissuealso rapidly absorbs the light 2575.

For example, in response to the laser light 2575, the ink 2580 may heatso rapidly as to cause a transformation of the tissue immediately underthe ink 2580, such as blackening, burning, charring, etc. Thetransformed tissue then readily interacts with the light 2575, and thetissue heats rapidly, burns, vaporizes, ablates, etc. Accordingly, awavelength that might not otherwise readily cut, ablate, burn, incise,vaporize, or remove tissue can be used in surgery to provide cutting,ablation, burning, incising, vaporization, or removal of tissue.

In one exemplary embodiment, the ink 2580 helps limit the depth of thetissue that is cut by the laser light. In some situations, surgeons mayapply the ink 2575 to a tissue surface that they wish to remove withoutharming the underlying tissue. For example, a surgeon might wish to killmalignant brain tumor cells without damaging nearby brain cellsassociated with an important brain function such as speech or eye sight.In this situation, the surgeon can insert the tip of the surgicalhandpiece 2530 into the brain at the tumor. After delivering the ink2545 (or as the ink is being delivered), the surgeon can deliver acontrolled burst of laser light 2575 that vaporizes or otherwise killsor destroys the tissue that is in direct contact the ink, while theunderlying tissue can remain relatively unaffected. That is, the tumorcells can be destroyed while a critical nerve or a group of brain cellsremains living or viable.

The system 2500 can comprise one or more transition layers 175 to helpmanage light flow at the various optical interfaces 275 that the system2500 comprises. Such optical interfaces 275 can comprise the distalsurface of the laser deliver optic 2550, the proximal end face of theoptical fiber 2520, the optics of the infrared laser 2505 that launchlaser light into the optical fiber 2520, or a mirror of the laser'slasing cavity, for example.

The infrared laser 2505 can be a semiconductor laser, an eximer laser, atunable laser, or a gas laser, for example. In one exemplary embodiment,the infrared laser 2505 is a Nd:YAG laser or some other laser thatoutputs light between about 600 nanometers and 3,500 nanometers.

The optical fiber 2520 typically comprises a glass fiber having a coreof about 600 to 1,000 microns and an outside cladding diameter of about680 to 1,200 microns. A sheath typically protects the fiber 2520 fromdamage and helps shield operating room personnel from scattered light inthe event that the fiber 2520 breaks or cracks. A tube 2525, such as acapillary tube, delivers the ink 2580 from the ink supply module 2510 tothe surgical handpiece 2530.

In one exemplary embodiment, the ink delivery tube 2515 and the fiber2520 are contained in a common sheathing or tube. In one exemplaryembodiment, the ink supply 2510 and the infrared laser 2505 are housedin a common enclosure along with a microprocessor or some othercomputing device that helps control the delivery of laser light 2575 andink 2545. In one exemplary embodiment, a sensor mounted at the distaltip of the surgical handpiece 2530 monitors the light-tissue interactionand/or the light-ink interaction. Monitoring information can feedback tothe microprocessor for controlling light and/or ink delivery. The tip ofthe surgical handpiece 2530 can comprise a Raman probe, a fluorescenceprobe, an infrared probe, or an imaging device. The imaging device cancomprise an optical coherence tomography (“OCT”) tip, an imaging bundleof fibers, an ultrasound device, etc. Such a chemical, spectroscopic, orimaging sensor can provide images for viewing by the surgeon or sensordata for automatic feedback control.

The surgical handpiece 2530 typically comprises buttons or triggers2535, 2540 through which the surgeon can control delivery of laser light2575 and ink 2580. The surgeon can engage, depress, or squeeze the lasertrigger 2535 to emit laser light 2575. Likewise, the surgeon can engage,depress, or squeeze the ink trigger to deliver ink 2580.

In one exemplary embodiment, the surgical handpiece 2530 comprises aknob or control for adjusting the rate of ink deliver. Also, thehandpiece 2530 can comprise an adjustable nozzle for controlling thespray pattern of ink delivery. Thus, the surgeon can control whether theink 2580 is delivered in a tight stream, in a mist, as a jet, or in someother pattern that the surgeon may desire for a particular surgicalsituation.

The light absorbing material or ink 2545 can comprise carbon,caramelized sugar, commercially available medical ink that is useful formarking incision lines in preparation for a surgical operation, an inkor colorant used for tattooing, a tattoo pigment, an organic orinorganic pigment, nano-particles, or a dye, to name a few examples. Theink 2545 can be viewed as an incision promoter or a compound thatstimulates or control light-tissue interaction to achieve a surgicalresult. The delivered compound can be a compound that exhibitsessentially no biological activity, rather than a drug that in and ofitself stimulates a therapeutic effect. In one exemplary embodiment, thesystem 2500 delivers a medical-grade solvent along with the lightabsorbing material, and the solvent promotes penetration of the ink 2545to a target tissue depth. In one exemplary embodiment, the system 2500comprises replaceable ink cartridges, similar to the cartridges of anink-jet printer.

Turning now to FIG. 26, this figure illustrates a flowchart of anexemplary process 2600 for cutting biological tissue by applying dye2580 and laser light 2575 to the tissue according to an embodiment ofthe present invention. As discussed above with reference to FIG. 25, oneor more steps of Process 2600, which is entitled Enhance Light-TissueInteraction, can comprise a transition layer structure 275 managinglight at an optical interface.

At Step 2610, a surgeon applies a light absorbing material, such as ink,dye, carbon, carbonized sugar, melanin, etc. to a tissue surface orboundary at which the surgeon desires to create an incision. The tissueboundary may be subcutaneous, for example within a body cavity or tissuestructure that the surgeon accesses endoscopically. The light absorbingmaterial can be comprise a solvent such as dimethyl sulfoxide (“DMSO”)that promotes penetration of the light-absorber into the tissue. Thelight absorbing material can be a material that absorbs light viainteraction between photons and the material's electron cloud.Alternatively, the interaction can involve chemical bond vibrations.

At Step 2620, the surgeon engages or prompts the laser system 2500 todeliver light, for example one or more pulses of light, to a selectedarea of tissue.

At Step 2630, in response to the surgeon's prompt, the gain medium ofthe laser 2505 energizes. Light resonates with the lasing cavity thatcan be bounded by a mirror comprising a series of transition layers 175.The surgical handpiece 2530 delivers the laser light 2575 to the tissuesurface or boundary.

At Step 2640, the light absorbing ink 2580 absorbs the laser light andablates, incises, cuts, vaporizes, damages, destroys, or removes theselected area of tissue. The light absorbing material helps create alight-tissue cascade or chain reaction. Such reaction can cause thetissue to rapidly react to the laser light 2575, via vaporization,boiling at a microscopic level, rapid expansion, burning, etc. The laserlight 2575 can have a red or an infrared wavelength that would achieveless desirable surgical results were it not for the application of theink 2580. Following Step 2640, Process 2600 ends.

A wide range of biological, medical, and biomedical applications,systems, and methods can benefit from managing light at an interfacebetween two optical media. For example, analytical instruments canincorporate transition layers 175 for such light management.

Turning now to FIG. 27, this figure illustrates a flowchart of anexemplary process 2200 for analyzing tissue of an organism via acquiringspectra from the tissue while modulating the tissue's blood content andusing the acquired spectra to compensate for blood content according toan embodiment of the present invention. The process 2200 is entitledModulate Blood Flow to Tissue to Cancel Blood Influence on TissueAnalysis. If the system that acquires the spectra uses light, forexample to acquire optical spectra, then the system can comprisetransition layers 175 for light management at one or more opticalinterfaces.

At Step 2710, an analytical system acquires a spectrum from a selectedsite of an organism and stores the spectrum in memory. The organism canbe a human, a mammal, or some other living thing. The analytical systemcan comprise an optical spectrometer, a Raman spectrometer, an OCTimaging device, a magnetic resonance system (“MRI”), a functional MRI, aCAT scanner, a CT-scanner, an infrared analyzer, a nuclear magneticresonance (“NMR”) system, a fluorescence instrument, a positive emissiontomography (“PET”) device, an ultrasound device, or an x-ray system, toname a few examples.

Blood flows freely to the selected site during or immediately precedingthe spectral acquisition. Accordingly, the tissue at the selected sitehas a rich or normal content of blood when the spectrum is acquired. Inone exemplary embodiment, the tissue site is artificially engorged withblood, for example via blocking a return vessel or by applying suctionthat will draw extra blood into the site.

Thus, the acquired spectrum comprises some contribution from the tissueitself and some contribution from the blood. In other words, thespectrum may have some structures that are associated with blood andsome structures that are associated with other cells or chemical in theorganisms. Such other cells or chemicals may comprise bone, muscularfibers, nerve cells, skin, hair, fat, artificial chemicals, drugs,pharmaceutical agents, brain cells, etc.

At Step 2720, transition layers 175 can manage light at any appropriateoptical interfaces 175 that the analytical system comprises. Suchoptical interfaces 175 might include one or more of a laser, an opticalfiber end face, a grating, a thin film filter, a light, an illuminationsystem, an optical memory, a optical disk, a machine readable mediumthat is readable via light, an endoscope, an optical spectrometer, etc.Nonetheless, some analytical systems might not comprise such opticalinterfaces.

At Step 2730, the analytical system reduces or suppresses blood contentin the selected tissue site. Various methods or systems can be used inconnection with reducing blood content of the selected tissue site, afew of which will be discussed below.

In one exemplary embodiment, blood flow can be restricted from the site.Restricting blood flow can involve a surgeon clamping a feeder artery,an apparatus automatically pressing a pressure point that restricts flowin a blood conduit, such an artery. A medical assistant or a machine canapply a tourniquet or an inflatable cuff or bladder around the tissuesite. In one exemplary embodiment, an air line can apply air pressure tothe site to compress capillaries or other blood conduits. (The air linecan also apply suction to drive blood into the site in connection withStep 2710 or some other step.)

In one exemplary embodiment, an application of a cold compress or icecan cause a capillary, artery, or vessel constriction. In one exemplaryembodiment, a drug can be administered to reduce blood flow or toconstrict capillaries. One such drug is nicotine.

In one exemplary embodiment, a beating heart can modulate the blood flowinto and out of the site. For example, Step 2710 can be executed withthe heart has driven blood into the tissue site. In this case, Step 2730can comprise the heart pulling blood out of that tissue site.

At Step 2740, the analytical system acquires a spectrum from theselected tissue site and stores that spectrum in memory. The acquisitionoccurs while the level of blood in the site is lower than the bloodlevel at Step 2710. That is, the analytical system can execute Step 2740in parallel with or immediately following Step 2730 so that bloodcontent of the tissue is at a reduced level during the spectralacquisition.

At Step 2750, that analytical system removes the stimulus that reducedblood content in the tissue at Step 2730. For example, the analyticalsystem or some human may automatically or manually heat the tissue sitethat had been cooled, remove an occlusion or restriction from a feederblood conduit, plug a draining blood conduit, remove a tourniquet, applysuction to the tissue site, etc. In one exemplary embodiment, theanalytical system not only removes the cause of the reduced content butalso stimulates blood flow into the tissue site. In one exemplaryembodiment, the analytical system waits until the blood content returnsto a normal level. In on exemplary embodiment, the analytical system orsome person administers a chemical, drug, or pharmaceutical agent thatincreases blood flow. Such a stimulant could comprise epinephrine oradrenalin/adrenaline, for example. In one exemplary embodiment, theblood content at Step 2750 can be substantially different than the bloodcontent at Step 2710.

At Step 2760, the analytical system has spectra that were acquired withthe tissue site having high blood content and at least one sampleacquired with the tissue having low blood content. The system may have adata analysis module that processes the spectrum acquired at Step 2710and the spectrum acquired at Step 2750. For example, the data analysismodule may average those spectra. Alternatively, the module may subtractthose spectra to obtain a difference spectrum.

The data analysis module then subtracts the spectrum acquired when theblood content was high (or an average of the two high-blood-contentspectra) from the spectrum acquired when the blood content was low. Inother words, the analytical system makes a comparison between a spectrumthat was acquired from the tissue and a relatively large amount of bloodand a spectrum that was acquired from the tissue and a relatively lowamount of blood. Accordingly, the data analysis module derives or infersa blood spectrum. That is, the analytical system produces a spectrumthat has structures that can be primarily associated with blood and/orchemicals present in that blood.

At Step 2770, the analytical system uses the blood spectrum fordiagnosis or for blood analysis. Such uses might include, among otherpossibilities, determining whether a particular blood protein, bloodgas, pharmaceutical agent, drug, surgical gas, metabolite, oranesthesia, is present in the blood. Another example could be evaluatingblood sugar or a glucose level. For example, an infrared or Ramananalyzer could reference-out the impact of the tissue from spectraacquired of a finger or an arm, to produce a blood spectrum. And, thatblood spectrum could be analyzed to determine blood sugar in connectionwith managing diabetes. Analyzing the blood spectra to determine bloodsugar could comprise partial least squares analysis, regressionanalysis, artificial intelligence, Kalman filtering, spectraldecomposition, or some other known spectral analysis.

At Step 2780, the analytical system acquires additional spectra from thetissue site. The spectral acquisition might be taken while the bloodcontent was at a natural level, at an artificially heightened level, orat an artificially suppressed level.

At Step 2790, the data analysis module of the analytical systemsubtracts the inferred blood spectra from each of the additionalspectra, thereby producing blood-compensated spectra. The data analysismodule can scale the inferred blood spectra, for example to bring aselected “marker” peak in the blood spectra to a height that matches orcorrelates with the height of a particular portion of the subsequentlyacquired spectra.

For example, the data analysis module can use a spectral decompositionto amplify the blood spectrum so that when the amplified blood spectrumis subtracted from the subsequently applied spectra, the bloodcontribution is removed from those spectra.

At Step 2795, the data analysis module compares the compensated spectrato a catalogue or a database of normal tissue spectra. The comparisonidentifies deviations from normal or anomalies, thereby automaticallyindicating a possibility of a disease, a condition, or a malignancy, forexample. The results can also be used for drug development, for exampleto help evaluate a pharmaceutical activity or the organism metabolizinga drug or some introduced chemical. Moreover, the results can aidadministering a therapy or conducting surgery or some other medicalprocedure.

Following Step 2795, Process 2200 ends.

Exemplary embodiments in which a material is analyzed via directing alight beam through a sample and collecting light emanating from thesample 2825 will now be discussed with reference to FIGS. 28 and 29. Ingeneral, the systems can comprise a reflector disposed circumferentiallyaround an illuminated portion of the sample. The illuminated portion ofthe sample can be cylindrical. The reflector can receive light emanatingradially outward from the illuminated cylinder, can form a beam from thereceived light, and can direct the beam to a light processor or a lightanalyzer, such as a spectroscopic system, that deduces information aboutthe sample based on the light.

Turning now to FIG. 28, this figure illustrates an exemplary opticalsystem 2800 for optically characterizing a sample 2825 according to anembodiment of the present invention. The system 2800 can be used foranalyzing biological samples, gas, wastewater, petroleum products, air,pollution, pharmaceutical materials, etc, manufacturing materials,feedstock, reactants, DNA samples, body fluids, etc.

The system 2800 comprises a laser 2805 that illuminates and/or energizesthe sample 2825, which might be a gas, a gel, a liquid, or a matrix, forexample. In one exemplary embodiment, the sample 2825 comprisesnanoparticles and biological materials, for example a composition of aliquid, a DNA sample, and gold particles that help induce an amplifiedsurface enhanced Raman scattering/spectroscopy (“SERS”) effect from theDNA sample. In one exemplary embodiment, the sample 2825 comprisesquantum dots, quantum dashes, or some form of artificially boundelectrons. Such quantum dots can be attached to a constituent or acomponent of the sample 2825 to help determine whether that componentbinds or reacts with another component of the sample 2825, for exampleto facilitate a DNA, protein, or enzyme analysis. The sample 2825 can bein situ, in vivo, ex vivo, extractive, native, natural, prepared, orman-made, for example.

The laser 2805 can have a wavelength that is selected to provide or toaccentuate a particular type of light-matter interaction. For example,the laser could be a green laser for conducting a Raman analysis ofhydrogen gas, a near infrared laser for conducting a Raman analysis of abiological material that is subject to interfering fluorescence, or anultraviolet (“UV”) laser for fluorescent analysis, UV-resonant Ramananalysis, or SERS.

The laser 2805 outputs a generally collimated beam 2815, typicallycomprising a cylinder of light propagating along an optical axis 2820.The beam 2815 thus illuminates a cylindrical portion of the sample 2825.After the laser beam 2815 passes through the sample 2825, a light trap2855 or some other absorber collects the beam 2815, primarily tominimize uncontrolled reflections that could interfere with the materialanalysis.

As the laser beam 2815 propagates through the sample 2825, the laserphotons interact with the sample 2815. The interaction can compriseRaman scattering, fluorescence, Mie scattering, SERS, elasticinteraction, inelastic interaction, UV-resonance Raman scattering,stimulated Raman scattering, lasing, amplification, particle scattering,molecular vibrations, vibration of electron clouds, near infraredabsorption, infrared absorption, or a combination thereof, to name a fewexamples.

The laser photons thus generate, stimulate, scatter, induce, or produceother photons from the sample, for example emitted from the sample viainelastic scattering. That is, in response to the laser beam 2815,emissions 2860 produce photons or emission rays 2865. At least a portionof those emission rays 2865 propagate radially outward from the laserbeam 2815. Thus, the emission rays 2865 include rays that essentiallyintersect the optical axis 2820, somewhat analogous to spokes from ancenter of a wheel.

The emission rays 2865 propagating radially outward are incident uponthe concave mirror 2810, which may have a form of an ellipsoid, aparaboloid, a revolved oval, an egg-shaped form, or an inwardly curvedsurface, to name a few examples. The concave mirror 2815, which has aport or an aperture 2830 for entry of the laser beam 2815, directs theemission rays 2865 to form a generally collimated beam 2850. Thediversion of the collimated beam 2850 is controlled or has somewhat of acylindrical shape, larger than the laser beam 2815.

More specifically, the emission rays 2865 propagate outward from thelaser beam 2815, generally perpendicular to the optical axis 2820, andintersect the contoured surface of the concave mirror 2810. Thecontoured mirror surface reflects, deflects, or diverts the emissionrays 2865 to provide redirected rays 2870 that collectively form thegenerally collimated beam 2850.

The mirror 2835 reflects the collimated beam 2850 at a generally rightangle. The mirror 2835 has a port or a hole 2840 through which the laserbeam 2805 passes. Alternatively, the mirror 2835 can comprise a dichroicoptic that transmits the laser beam 2815 and reflects the collimatedbeam 2850 that is shifted in wavelength with respect to the laser light.Such a dichroic optic can comprise transition layers 175, as discussedabove.

After being redirected by the mirror 2835, the collimated beam 2850 isincident upon the filter 200, discussed above with reference to FIG. 2.The filter 200 typically comprises a notch filter that reflects anylaser light present in the collimated beam 2850 and transmitswavelength-shifted light associated with the emissions 2860, for exampleStokes and/or anti-Stokes light. Accordingly, the filtered beam 2875 isprincipally composed of the emission rays 2870, and the beam 2875 has awell-defined or well-controlled geometric form.

The light processor 2880 receives the filtered beam 2875 and analyzesthat beam 2875 to characterize the sample 2825. In one exemplaryembodiment, the light processor 2880 comprises a spectrometer,spectrograph, or spectrophotometer based on a volume holographictransmission grating. In such an embodiment, the light processor 2880can produce digitally recorded spectra of the emissions 2860. Candidatesuppliers of such a light processor 2880 include Process Instruments,Inc. of Salt Lake City, Utah or Kaiser Optical Systems, Inc. of AnnArbor, Mich. Thus, the light processor 2880 can separate the collimatedbeam 2850 into constituent wavelengths, measure the relative intensitiesof those constituent wavelengths, and determine the composition of thesample 2825 based on those measured intensities. For example, the system2800 can determine biological information, such as DNA analysis, abiochemical reaction, or a drug activity, based on spectrographicanalysis of the filtered light beam 2875.

In one exemplary, a process or method can be associated with the system2800. That is, certain steps can involve the system 2800 to produce amaterial analysis. For example a method of light-based characterization,can comprise the steps of: (a) introducing particles, comprisingartificially bound electrons, into a material; (b) directing essentiallyparallel rays of laser light, along an excitation axis, through thematerial; (c) responsive to the directing step, emitting rays ofresponse light from the particles at locations along the excitationaxis, the rays of response light substantially perpendicular to theexcitation axis; (d) reflecting the emitted rays of the response lightwith a concave mirror having an optical axis essentially collinear withthe excitation axis; (d) forming a bundle of essentially parallel raysof the response light, substantially aligned with the excitation axis,in response to the reflecting step; (e) separating the bundle ofessentially parallel rays of the response light from the essentiallyparallel rays of the laser light; (f) filtering the bundle ofessentially parallel rays of the response light; (e) coupling thefiltered response light into a spectrograph; and (f) spectrallycharacterizing the response light.

In one exemplary embodiment, the introduced particles can comprisequantum dots. In one exemplary embodiment the response light is shiftedin wavelength from the laser light.

In one exemplary embodiment, the method further comprises the steps of:(i) attaching at least one of the quantum dots to a component of thematerial if the component has an affinity for attachment; and (ii)determining whether the response light indicates attachment of the onequantum dot to the component in response to the spectrallycharacterizing step.

In one exemplary embodiment, a system for light-based characterizationof particles can comprise: (a) an optical source that outputs a firstbeam through a sample comprising particles, wherein light emanates fromthe particles in response to the first beam; (b) a contoured mirror,circumferentially disposed around the illumination beam, operative toshape the emanated light into a second beam; (c) a light separatoroperative to separate the first beam from the second beam; and (d) adetector operative to detect a wavelength of the second beam.

In one exemplary embodiment, the particles comprise nanoparticles orquantum dots. In one exemplary embodiment, at least one of the particlesis a molecule. In one exemplary embodiment, the light separatorcomprises a filter and the detector comprises a grating operative todisperse the second beam for reception by a detector array. In oneexemplary embodiment, the light separator comprises an interferencefilter and wherein the first beam and the second beam are incident onthe filter. In one exemplary embodiment, the light emanates from theparticles via Raman scattering or fluorescence. In one exemplaryembodiment, the light emanates from the particles in response toexcitation of an artificially trapped electron of the particle. In oneexemplary embodiment, the first beam and the second beam propagate in anunconfined manner along essentially co-linear optical axes. In oneexemplary embodiment, the emanated light propagates in a substantiallyperpendicular direction, with respect to the first beam, between thefirst beam and the contoured mirror. In one exemplary embodiment, theemanated light emanates from the particles disposed in the first beamalong a longitudinal section of the first beam.

In one exemplary embodiment, a second method for analyzing a materialcomprises the steps of: (a) emitting from a cylindrical volume of thematerial a first light, propagating radially, in response toilluminating the cylindrical volume with a second light; (b) forming abeam comprising the first light in response to reflecting the radiallypropagating first light; (c) separating the beam of the first light fromthe second light; and (d) analyzing the separated first light.

In one exemplary embodiment of the second method, the cylindrical volumecomprises emitting a beam, comprising the second light, through thecylindrical volume. In one exemplary embodiment of the second method,the beam comprising the first light is a collimated beam, andilluminating the cylindrical volume comprises directing a substantiallycollimated beam that comprises the second light through the material. Inone exemplary embodiment of the second method, reflecting the radiallypropagating first light comprises reflecting the radially propagatingfirst light with a concave mirror having an optical axis that passesthrough the cylindrical volume. In one exemplary embodiment of thesecond method, the beam of the first light comprises collimated lightpropagating in free space. In one exemplary embodiment of the secondmethod, the material comprises nanoparticles, and the emitting stepfurther comprises emitting the first light from the nanoparticles. Inone exemplary embodiment of the second method analyzing the separatedfirst light comprises conducting a spectral analysis. In one exemplaryembodiment of the second method, the second light comprises laser light,illuminating the cylindrical volume with the second light comprisesilluminating the cylindrical volume with essentially parallel rays ofthe laser light, and the beam comprises essentially parallel rays of thefirst light.

Turning now to FIG. 29, this figure illustrates an exemplary opticalsystem 2900 for optically characterizing a sample 2825 according to anembodiment of the present invention. The system 2900 comprises aresonant or semi-resonant optical cavity 2975 or etalon between thepartial reflector 2925 adjacent the laser 2805 and the partial reflector2926 located at a standoff distance from the laser 2805. The partialreflectors 2805, 2806 can provide broadband reflectivity oralternatively can reflect a narrow range of colors or wavelengths, whiletransmitting other colors or wavelengths outside that range.

The cavity 2975 sets up a standing wave between the partial reflectors2805, 2806 that imparts the laser beam 2815 with higher intensity in thecavity 2975 that outside the cavity 2915. Thus, the cavity 2975 can beviewed as providing an intensified or amplified region of the laser beam2815. Outside the cavity 2975, the mirror 2935 diverts the laser beam2815 (outside the amplified cavity region) to the light trap 2855.

In one exemplary embodiment, the laser intensity in the cavity 2975 issufficient to excite the sample 2825 to a lasing, near lasing, or astimulated state. That is, the laser 2805 can pump the sample 2825towards causing the sample 2825 to lase or to emit stimulated radiation.In one exemplary embodiment, the lasing cavity of the laser 2805 extendsto the partial reflector 2925, thereby providing a lasing cavity thatthe mirrored surface 2910 surrounds.

Whether via spontaneous emissions, stimulated emissions, scattering, orsome other interaction between matter and photonic radiation, the laserlight in the cavity 2975 provides emissions 2860 and associated lightrays 2865 that travel outward from the optical axis 2820. The contouredmirror 2910 that circumferentially surrounds the cavity 2975 and theilluminated sample 2825 collimates the light rays 2865 and directs themtowards spectrometer 2980, as the beam 2850. That is, the concave mirror2910 reflects the emission rays 2865 to create a beam 2850 ofessentially or generally parallel rays headed towards the spectrometer2980.

The filter 200, discussed above as an exemplary embodiment, rejectsresidual laser light and transmits the light that is wavelength shifted,e.g. to the red or to the blue, as the filtered beam 2875. Thespectrometer 2980, which can be a spectrophotometer, creates a digitalspectrum of the emitted light 2865 that can characterize the sample 2825or some property thereof. The spectrometer 2980 typically comprises oris linked to a computing system that performs spectral analysis and thatincludes a data storage device, a processor, and spectral analysissoftware.

Thus, the system 2900 can evaluate the sample 2825 based on the relativewavelength intensities of the emitted or scattered light 2865 thatemanates radially outward from the portion of the sample 2825 disposedin the cavity 2975.

In summary, the present invention can support managing light at anoptical interface to benefit a wide range of devices, processes, andapplications—a representative few of which have been discussed above asexamples.

From the foregoing, it will be appreciated that the present inventionovercomes the limitations of the prior art. Those skilled in the artwill appreciate that the present invention is not limited to anyspecifically discussed application or implementation and that theembodiments described herein are illustrative and not restrictive. Fromthe description of the exemplary embodiments, equivalents of theelements shown herein will suggest themselves to those skilled in theart, and ways of constructing other embodiments of the present inventionwill appear to practitioners of the art. Therefore, the scope of thepresent invention is to be limited only by the claims that follow.

What is claimed is:
 1. An optical filter comprising: a series of thinfilm optical interfaces, each formed between a respective high indexthin film layer and a respective low index thin film layer; and arespective series of transition layers of alternating refractive indicesdisposed at each thin film optical interface in the series of thin filmoptical interfaces, each respective series of transition layerscomprising: high index transition layers disposed in one of therespective low index thin film layers; and low index transition layersdisposed in one of the respective high index thin film layers, andwherein the high index thin film layers and low index thin film layersand the series of transition layers of alternating refractive indicescollectively provide a sinusoidal variation in refractive index orcollectively provide a refractive index profile having the form of asquare wave with rounded corners.
 2. The optical filter of claim 1,wherein the high index transition layers and the high index thin filmlayers have common compositions.
 3. The optical filter of claim 1,wherein one or more of the high index transition layers and one or moreof the high index thin film layers have a common composition.
 4. Theoptical filter of claim 1, wherein a particular thin film opticalinterface is formed between a particular low index thin film layerhaving a first refractive index and a particular high index thin filmlayer having a second refractive index, wherein the series of transitionlayers disposed at the particular thin film optical interface compriseshigh index transition layers of the second refractive index disposed inthe particular low index thin film layer.
 5. The optical filter of claim1, wherein a particular thin film optical interface is formed between aparticular low index thin film layer having a first refractive index anda particular high index thin film layer having a second refractiveindex, wherein the series of transition layers disposed at theparticular thin film optical interface comprises low index transitionlayers of the first refractive index disposed in the particular highindex thin film layer.
 6. The optical filter of claim 1, comprising lowindex transition layers no thicker than about ten nanometers and highindex transition layers no thicker than about ten nanometers.
 7. Theoptical filter of claim 1, wherein one or more of the low indextransition layers and one or more of the low index thin film layers havea common composition.
 8. The optical filter of claim 1, wherein one ofthe low index transition layers and one of the low index thin filmlayers comprise a first refractive index, and wherein one of the highindex transition layers and one of the high index thin film layerscomprise a second refractive index that is substantially higher than thefirst refractive index.
 9. The optical filter of claim 1, wherein eachone of the low index transition layers of at least one of the series oftransition layers of alternating refractive indices is thinner than theprevious low index transition layer of the series.
 10. The opticalfilter of claim 1, wherein each one of the high index transition layersof at least one of the series of transition layers of alternatingrefractive indices is thinner than the previous high index transitionlayer of the series.
 11. An optical filter comprising: high index thinfilm layers interleaved with low index thin film layers to form aperiodic series of optical interfaces; and a respective system ofalternating refractive index transition layers disposed at each of theoptical interfaces, each system of alternating refractive indextransition layers comprising: high index transition layers disposed inone of the interleaved low index thin film layers; and low indextransition layers disposed in one of the interleaved high index thinfilm layers, and wherein the high index thin film layers interleavedwith low index thin film layers and the systems of alternatingrefractive index transition layers collectively provide a sinusoidalvariation in refractive index or collectively provide a refractive indexprofile having the form of a square wave with rounded corners.
 12. Theoptical filter of claim 11, wherein each of the high index transitionlayers has a respective thickness that is less than ten nanometers, andwherein each of the low index transition layers has a respectivethickness that is less than ten nanometers.
 13. The optical filter ofclaim 11, wherein each system of alternating refractive index layerscomprises progressively thinner layers.
 14. The optical filter of claim11, wherein each respective one of the high index transition layers ofone of the systems of alternating refractive index transition layers isthinner than the previous respective one of the high index transitionlayers in the system, such that the high index transition layers of thesystem are progressively thinner.
 15. The optical filter of claim 11,wherein each respective one of the low index transition layers of one ofthe systems of alternating refractive index transition layers is thinnerthan the previous respective one of the low index transition layers inthe system, such that the system comprises progressively thinner lowindex transition layers.
 16. An optical filter comprising: a periodicarrangement of optical interfaces, individually operative to transmitand reflect incident light and collectively operative to filter lightvia optical interference, wherein each of the optical interfaces isformed between two respective layers of optical materials havingcontrasting refractive indices, with a respective series of transitionlayers of contrasting refractive index extending across each of theoptical interfaces, wherein each respective series of transition layerscomprises: a first plurality of transition layers disposed in a first ofthe two respective layers of optical materials; and a second pluralityof transition layers disposed in a second of the two respective layersof optical materials, and wherein the layers of optical materials havingcontrasting refractive indices and series of transition layers ofcontrasting refractive index collectively provide a sinusoidal variationin refractive index or collectively provide a refractive index profilein the form of a square wave with rounded corners.
 17. The opticalfilter of claim 16, wherein each respective series of transition layersis periodic.
 18. The optical filter of claim 16, wherein the firstplurality of transition layers and the second of the two respectivelayers have substantially common refractive indices, and wherein thesecond plurality of transition layers and the first of the tworespective layers have substantially common refractive indices.
 19. Theoptical filter of claim 16, wherein the first plurality of transitionlayers and the second of the two respective layers have substantiallycommon composition, and wherein the second plurality of transitionlayers and the first of the two respective layers have substantiallycommon composition.
 20. The optical filter of claim 16, wherein each ofthe first plurality of transition layers disposed in the first of thetwo respective layers of optical materials is less than about tennanometers in thickness.